melissa!s.!duvall! - vcrlter.virginia.edu ·...
TRANSCRIPT
!!!
!!
The!Effects!of!Waves!and!Tidal!Inundation!on!Sediment!Deposition!and!Flux!across!a!Bay=Marsh!Boundary!
!!!
!!
Melissa!S.!Duvall!Annapolis,!Maryland!
!!!
B.S.,!Environmental!Science!and!Policy,!University!of!Maryland,!2010!!!
!!!
A!thesis!presented!to!the!Graduate!Faculty!of!the!!University!of!Virginia!in!Candidacy!for!the!degree!of!!
Master!of!Science!!!
Department!of!Environmental!Sciences!!!
University!of!Virginia!August,!2014!
!! !
!
!
ii!
Abstract(
Sediment!deposition!processes!acting!on!salt!marshes!adjacent!to!larger!
bodies!of!water,!such!as!bays,!differ!from!the!processes!acting!in!tidal!creek!
marshes,!but!have!not!been!well!characterized!by!previous!research.!This!difference!
in!interface!alters!the!primary!controls!on!suspended!sediment!concentration!(SSC),!
an!indication!of!sediment!availability,!as!well!as!sediment!flux!to!and!deposition!on!
the!marsh.!This!study!was!conducted!along!the!boundary!between!a!shallow,!
microtidal!coastal!lagoon,!Hog!Island!Bay,!and!a!microtidal!salt!marsh!on!the!edge!of!
Chimney!Pole,!a!marsh!island!on!the!Eastern!Shore!of!Virginia.!This!research!sought!
to!characterize!the!hydrologic!regime!at!the!bay=marsh!boundary,!determine!
changes!in!SSC!due!to!changing!wave=generated!bottom!shear!stress,!establish!the!
effect!of!tides!and!currents!on!sediment!transport!to!the!marsh,!and!estimate!
changes!in!bottom!shear!stress!due!to!relative!sea!level!rise!(RSLR)!and!storm!surge.!!
Two!primary!differences!in!bay!and!tidal!creek!environments!are!the!
presence!of!waves!and!unconstrained!flow.!The!results!from!this!study!indicate!a!
strong!correlation!between!wind!direction!and!wave!formation,!whereby!the!largest!
waves!formed!when!westerly!winds!(i.e.!the!direction!of!longest!fetch)!blew!across!
Hog!Island!Bay!at!relatively!high!speeds!(>!8!m!s=1).!Maximum!wave=generated!bed!
shear!stress!on!the!tidal!flat!during!times!of!strong!westerly!winds!occurred!at!
water!elevations!near!the!marsh!platform!height!(~0.5!m!above!MSL),!above!which!
shear!stress!declined.!Our!findings!showed!that!waves!primarily!force!SSC,!but!the!
impact!of!wave!events!on!sediment!deposition!at!Chimney!Pole!is!limited!by!the!fact!
that!these!events!typically!occur!when!the!marsh!is!not!flooded.!When!the!marsh!is!
!
!
iii!
flooded,!wave!height!is!rapidly!diminished!as!waves!propagate!across!the!bay=
marsh!boundary!due!to!vegetation!and!shallow!water!depths.!Modeling!changes!in!
wave=induced!bed!shear!stress!with!depth!revealed!that!shear!stress!is!likely!
approaching!a!maximum!given!present=day!sea!level,!wind!and!tidal!conditions.!If!
the!marsh!keeps!pace!with!RSLR,!sediment!deposition!will!be!maximized!by!
present=day!conditions!or!slow!RSLR.!However,!if!the!marsh!elevation!remains!
constant,!potential!deposition!may!increase!with!increasing!RSLR!and!storm!surge.!!
Winds!also!forced!currents,!whereby!weaker,!southerly!winds!were!
associated!with!an!alternating!northward!flood,!southward!ebb!current!pattern,!
whereas!strong,!northerly!winds!pushed!currents!southward!regardless!of!tidal!
phase.!Overall,!the!unconstrained!flow!present!in!Hog!Island!Bay!limited!sediment!
deposition!on!Chimney!Pole,!because!currents!carried!sediment!towards,!but!also!
away!from,!the!marsh!during!flooding!conditions.!High!bed!shear!stress!likely!
prevented!sediment!transported!onto!the!marsh!from!depositing!near!the!marsh!
edge;!therefore!it!was!deposited!further!into!the!marsh!interior.!Calculated!(0.025!g!
cm=2)!and!measured!(0.028!g!cm=2)!deposition!for!the!March!2014!deployment!
showed!that!the!marsh!is!accreting!further!away!from!the!edge.!The!results!
indicated!that!bed!shear!stress!was!sufficient!to!remobilize!sediment!after!it!
deposited,!however!grain!size!analysis!revealed!that!this!process!is!likely!limited!by!
bed!cohesiveness!at!the!site.!!
!!
! !
!
!
iv!
Acknowledgements(
( Thank!you!to!my!advisor,!Pat!Wiberg,!and!committee!members,!Matt!Kirwan!
and!Matt!Reidenbach,!for!the!advice!and!support!given!to!me!throughout!my!time!at!
UVA;!the!Reidenbach!lab!for!sharing!instruments!and!wind!data!needed!to!complete!
this!project;!the!boat!drivers!at!the!shore!(David,!Pat,!and!Chris)!for!braving!the!
winter!chill!on!the!ride!out!to!Chimney!Pole;!Ross!Timmerman!for!instrumentation!
troubleshooting;!Alia!Al=Haj!for!PSA!help;!Amanda!Timmerman!for!assisting!with!
field!work;!grad!students!for!their!friendship!and!the!memories;!the!NSF!Long=Term!
Ecological!Research!Program!at!the!Virginia!Coast!Reserve!and!the!UVA!Department!
of!Environmental!Sciences!for!financial!support;!God;!as!well!as!my!family!and!
Naveed!for!their!love!and!encouragement!in!all!my!endeavors.!!!
!
!
!
v!
Table(of(Contents!Abstract……………………………………………………………………………………………………………ii!! !Acknowledgements…………………………………………………………………………………….........iv!Table!of!Contents………………………………………………………………………………………………v!List!of!Figures………………………………………………………………………………………………..viii!List!of!Tables…………………………………………………………………………………………………….x!!!Chapter!1:!Introduction!! 1.1!Objectives………………………………………………………………………………………...2!
1.2!Study!Motivation………………………………………………………………………………3!! 1.3!Background! !! ! Wind=Waves………………………………………………………………………………..5!! ! Currents……………………………………………………………………………………...6!! ! Suspended!Sediment!Concentration……………………………………………..6!! ! Shear!Stress!on!Tidal!Flats…………………………………………………………...7!! ! Edge!Erosion……………………………………………………………………………….9!! ! Aboveground!Marsh!Vegetation……………………………………………...…10!! ! Sea!Level!Rise!&!Changing!Waves………………………………………………10!! 1.4!Site!Description……………………………………………………………………………...11!! 1.5!Approach………………………………………….……………………………………………15!!!Chapter!2:!Effect!of!Wind!on!Currents!and!Waves!! 2.1!Objectives…………………………………………..………………………………………….17!! 2.2!Methods—Data!Collection!and!Analysis.!!! ! Water!Depth!&!Storm!Surge………………………………………………...…….18!! ! Currents……………………………………………..…………………………………….18!! ! Wind!Waves……………………………………………..……………………………....19!! 2.3!Methods—Calculations!! ! Current=generated!Bottom!Shear!Stress……………………………………..20!! ! Wave=generated!Bottom!Shear!Stress………………………………………...20!! 2.4!Results!! ! Water!Depth!&!Storm!Surge……………………………………………………….21!
Currents!(Transect!A)!……………………………………………………………….24!Currents!(Transect!B)!……………………………………………………………….28!Effect!of!Edge!Morphology!on!Currents………………………………………31!
! ! Wind!Waves………………..…………………………………………………………….32!! ! Shear!Stress!Regimes………………………………………………………………...37!! ! Seasonal!Variations!in!Wind!and!Waves……………………………………..42!! 2.5!Discussion!! ! Water!Depth!&!Storm!Surge……………………………………………………….44!
Currents!(Transect!A)!……………………………………………………………….45!Currents!(Transect!B)!……………………………………………………………….46!Effect!of!Edge!Morphology!on!Currents……………………………………....47!Sediment!Advection!onto!the!Marsh…………………………………………...47!
!
!
vi!
! ! Wind!Waves……………………………………………..………………………………..48!! ! Shear!Stress!Regimes…………………………………………………………………49!! ! !!Chapter!3:!Effects!of!Tides,!Waves!and!Currents!on!Sediment!Resuspension,!Flux,!and!Deposition! !! 3.1!Objectives……………………………………………………………………………………….51!
3.2!Methods—Data!Collection!and!Analysis!! Measured!Sediment!Deposition…………………………………………………..51!! Sediment!Characteristics…………………………………………………………….52!! Biomass!Sampling………………………………………………………………………53!! Sediment!Resuspension……………………………………………………………...53!! OBS!Calibration…………………………………………………………………………..54!3.3!Methods—Calculations!!! Settling!Velocity………………………………………………………………………….55!! SSC!Profile………………………………………………………………………………….56!! Sediment!Flux!&!Calculated!Deposition……………….……………………….57!3.4!Results!! Measured!Sediment!Deposition…………………………………………………...58!! Sediment!Characteristics……………………………………………………………..59!! Sediment!Resuspension……………………………………………………………....61!! SSC!on!the!Marsh………………………………………………………………………...64!! Sediment!Flux!!&!Calculated!Deposition……………………………………….65!3.5!Discussion!! Sediment!Deposition…………………………………………………………………...71!! Sediment!Characteristics……………………………………………………………..72!! Sediment!Resuspension……………………………………………………………....73!! SSC!on!the!Marsh………………………………………………………………………...74!! Sediment!Flux!&!Calculated!Deposition….…………………………………….75!!!
Chapter!4:!Estimating!Changes!in!Potential!Deposition!due!to!Sea=Level!Rise!&!Storm!Surge!! 4.1!Objectives………………………………………………………………………………………..77!! 4.2!Methods—Calculations!! ! Calculated!Wave!Conditions………………………………………………………..77(! ! Bottom!Orbital!Velocity!and!Wave!Shear!Stress……………………………79!! ! Currents……………………………….………….…………………………………………80!! ! SSC……………………………………………………….…………………………………….81!! 4.3!Results!! ! Wave!Conditions………………………….………………………….…………………..81!
Currents………………………….………………………….……………………………….85!SSC………………………….………………………….……………………………………….87!Effect!of!Water!Depth!on!Wave=Generated!Bed!Shear!Stress………….88!Effect!of!Water!Depth!on!Potential!Deposition………………………………89!
! 4.4!Discussion!
!
!
vii!
! ! Wave!Conditions………………………………………………………………………….91!Effect!of!Water!Depth!on!Wave=Generated!Bed!Shear!Stress………….92!Effect!of!Water!Depth!on!Potential!Deposition………………………………95!
!!Conclusions………………………………………………………………………………………………………97!!!Works!Cited……………………………………………………………………………………………………100!!!Appendix!1:!OBS!Calibration!Equations……………………………………………………………106!!!Appendix!2:!Grain!Size!Distribution…………………………………………………………………109!!
!
!
viii!
List(of(Figures!!Figure!1.1! Conceptual!Model!of!Tidal!Creek!Marsh………………………………………….4!Figure!1.2! Conceptual!Model!of!Marsh!Island………………………………………………….5!Figure!1.3! Site!Map!Overview……………………………………………………………………….13!Figure!1.4! Zoomed=In!Site!Map……………………………………………………………………..14!Figure!1.5! Instrument!Deployment!Timeline…………………………………………………16!((Figure!2.1! Depth!Change!along!Transect!B…………………………………………………….22!Figure!2.2! Depth!Change!along!Transect!A…………………………………………………….23!Figure!2.3! Evidence!of!Storm!Surge……………………..………………………………………..24!Figure!2.4! Average!Water!Column!Currend!Direction!&!Speed!at!TAF…………….26!Figure!2.5! Upper!Water!Column!Current!Direction!&!Speed!at!Transect!A………27!Figure!2.6! Average!Water!Column!Current!Direction!&!Speed!at!TBF…………......29!Figure!2.7! Upper!Water!Column!Current!Direction!&!Speed!at!Transect!B………30!Figure!2.8! Effect!of!Edge!Morphology!on!Current!Direction!&!Speed……………....32!Figure!2.9! Change!in!Significant!Wave!Height!with!Wind!Speed!&!Direction……34!Figure!2.10! Change!in!Significant!Wave!Height!with!Wind!Speed!&!Direction……35!Figure!2.11! Change!in!Height!as!Waves!Propagate!onto!the!Marsh…….……………...36!Figure!2.12! Significant!Wave!Height!&!Depth!at!TAF,TBF,!&!TBB………………………37!Figure!2.13! Bottom!Shear!Stress!at!Transect!B!(Nov=Dec!2013)…………...…………...39!Figure!2.14! Bottom!Shear!Stress!at!Transect!B!(Mar!2014)………………………………40!Figure!2.15! Cumulative!Distribution!of!Bottom!Shear!Stress!at!Transect!B………..41!Figure!2.16! Current!Shear!Stress!as!a!function!of!Tidal!Range!at!TBF………………..41!Figure!2.17! Total!Shear!Stress!as!a!function!of!Depth!at!TBF………………………….....42!Figure!2.18! Dominant!Wind!Direction!during!Deployments……………………………...43!!!Figure!3.1! Example!of!Calibration!Curve………….…………………………………………….55!Figure!3.2! Cumulative!Distribution!of!Grain!Size…..………………………………………..60!Figure!3.3! Change!in!SSC!with!Significant!Wave!Height…………………………………..62!Figure!3.4! SSC!at!Transect!B………………………………………………………………………….63!Figure!3.5! Change!in!SSC!with!Wave!Shear!Stress!at!TBI!and!TBB…………………..64!Figure!3.6! Estimated!SSC!at!TBF!using!the!Rouse!Equation…………………………….67!Figure!3.7! Estimated!SSC!at!TAF!using!the!Rouse!Equation…………………………….68!Figure!3.8! Sediment!Flux!at!TBF……………………………………………………………………69!Figure!3.9! Sediment!Flux!at!TAF……………………………………………………………………70!!!Figure!4.1! Modeled!Significant!Wave!Height!at!TAF………………………………………..82!Figure!4.2! Modeled!Significant!Wave!Height!at!TBF………………………………………..83!Figure!4.3! Modeled!&!Recorded!Wave!Height!at!TAF!by!Wind!direction………….84!Figure!4.4! Modeled!&!Recorded!Wave!Height!at!TBF!by!Wind!direction………….85!Figure!4.5! Modeled!Currents………………………….…………….………………………………..86!Figure!4.6! Modeled!SSC!from!Modeled!Waves!&!Currents……………………………….88!
!
!
ix!
Figure!4.7! Estimated!Future!Changes!in!Wave!Shear!Stress……………………………89!Figure!4.8! Estimated!Future!Changes!in!SSC…………………………………………………..90!Figure!4.9! Estimated!Future!Changes!in!Sediment!Mass…………………………………91!Figure!4.10! Cumulative!Distribution!of!Wind!Speed!&!Direction!&!Depth………….94!( !
!
!
x!
List(of(Tables!!Table!2.1! Location!and!Elevation!of!Sampling!Stations………………………………….17!Table!2.2! Storm!Surge!frequency!&!Average!Surge……………………………………….23!Table!2.3! Distribution!of!Significant!Wave!Height!by!Deployment………………...43!Table!2.4! Summary!of!Key!Findings!and!Results!for!Chapter!2……………………...44!! ! ! ! !Table!3.1! Sediment!Deposition!Plate!Measurements!at!Transect!B………………..59!Table!3.2! Grain!Size!Analysis……………………………………………………………………….60!Table!3.3! Water!&!Organic!Content!in!Sediment!&!Biomass!Measurements.......60!Table!3.4! Calculated!Sediment!Deposition……………………………………………………70!Table!3.5! Comparison!of!Meas.!Dep.!at!Chimney!Pole!&!Philips!Creek……………72!(Table!4.1! Average!Fetch!for!TAF!&!TBF………………………………………………………...94!(!
!
!
1!
Chapter(1:(Introduction(
Intertidal!salt!marshes!are!among!the!world’s!most!biologically!productive!
and!economically!valuable!ecosystems!(Day!et!al.!1989).!Marshes!sequester!carbon,!
improve!water!quality,!and!protect!highly!populated!coastal!land!from!storm!surge!
and!erosion!(Day!et!al.!1989).!!Tidal!marsh!loss!has!accelerated!in!recent!decades!on!
a!global!scale,!resulting!in!estimated!losses!between!a!quarter!to!a!half!of!total!
marsh!area!(WHO!2005).!Whether!marshes!survive!SLR!depends!on!their!ability!to!
build!elevation!through!the!accumulation!of!organic!material!and!deposition!of!
mineral!sediment!(Friedrichs!&!Perry!2001).!!
Suspended!sediment!concentration!(SSC),!a!common!proxy!for!sediment!
availability,!strongly!influences!marsh!accretion!rates!(Kirwan!et!al.!2010).!In!the!
Virginia!Coast!Reserve!(VCR),!a!barrierTlagoonTmarsh!system!on!the!Atlantic!side!of!
the!lower!Delmarva!Peninsula,!creeks!supply!only!small!amounts!of!sediment!into!
the!system!(Lawson!et!al.!2007).!Therefore,!wind!waves!primarily!determine!SSC!by!
resuspending!sediment!from!bay!bottoms!(Lawson!et!al.!2007)!and!eroding!marsh!
edges!(McLoughlin!et!al.!2014).!Field!measurements!indicate!significant!spatial!and!
temporal!variations!in!SSC!in!shallow!bays!and!tidal!creeks!(Lawson!et!al.!2007;!
Christiansen!et!al.!2000),!driven!in!part!by!storm!surge!and!episodically!high!wave!
conditions.!!
Transport!of!suspended!sediment!from!bays!and!creeks!onto!marsh!surfaces!
depends!upon!current!magnitude!and!direction,!and!water!surface!elevation.!
Sediment!deposition!on!marsh!surfaces!depends!on!SSC,!inundation!time,!and!
sediment!settling!rates,!as!well!as!the!effect!of!vegetation!on!flow!velocity,!
!
!
2!
turbulence,!and!wave!dissipation.!This!research!seeks!to!better!understand!the!
factors!influencing!sediment!exchange!across!bayTmarsh!boundaries!and!deposition!
rates!on!marsh!surfaces.!Through!better!understanding!these!relationships,!we!will!
improve!our!ability!to!model!and!predict!marsh!vulnerability!to!future!increases!in!
sea!level!and!storminess.!!!
!
1.1.(Objectives(
( The!goal!of!this!research!is!to!examine!temporal!changes!in!SSC!over!tidal!
flats!as!well!as!the!conditions!under!which!this!sediment!is!deposited!on!bordering!
marsh!surfaces.!Marsh!boundaries!that!differ!in!edge!properties,!such!as!longTterm!
erosion!rates!and!scarp!profile,!are!investigated.!The!four!overarching!questions!
that!this!research!addresses!are:!!
• What!is!the!effect!of!wind!on!wave!formation!and!current!magnitude!and!
direction!on!shallow!tidal!flats!and!bordering!salt!marshes?!(Ch.!2)!
• What!changes!in!SSC!occur!over!tidal!flats!due!to!changing!wave!height!and!
water!depth!during!a!tidal!cycle?!(Ch.!3)!
• What!is!the!effect!of!tides!and!currents!on!sediment!transport!from!a!bay!to!
an!adjacent!marsh!surface?!!(Ch.!3)!
• What!impact!will!21st!century!SLR,!stronger!coastal!storms,!and!
accompanying!changes!in!wave!conditions!have!on!mineral!sediment!
deposition!on!marsh!islands?!(Ch.!4)!
These!objectives!are!addressed!in!the!chapters!listed.!!
(
!
!
3!
1.2(Study(Motivation(
The!longTterm!stability!of!salt!marshes!depends!on!the!interaction!between!
primary!production,!sediment!accretion,!land!elevation,!and!sea!level!(Morris!et!al.!
2002).!Marshes!rely!on!macrophytes!to!maintain!their!elevation!by!accumulating!
organic!material!and!trapping!mineral!sediment.!The!volume!of!sediment!trapped!or!
deposited!on!the!marsh!surface!depends!partly!on!the!amount!of!sediment!in!the!
water!column.!Threshold!rates!of!relative!sea!level!rise!(RSLR)!that!trigger!marsh!
drowning!depend!strongly!on!SSC!(Kirwan!et!al.!2010).!Therefore,!it!is!important!to!
understand!both!the!amount!of!sediment!entering!the!water!column,!its!source,!and!
the!trajectory!of!that!sediment!once!it!is!suspended.!!
The!previous!work!of!Christiansen!et!al.!(2000),!who!characterized!the!
factors!influencing!sediment!deposition!in!a!relatively!lowTenergy!tidal!creek!marsh!
(fig!1.1),!provides!the!primary!motivation!for!this!project.!Rather!than!focusing!on!
tidal!creek!marshes,!the!overarching!concern!of!this!project!is!to!understand!
depositional!processes!at!a!bayTmarsh!boundary.!
In!tidal!creek!marshes,!taller!and!thicker!vegetation!along!the!creek!bank!
slows!flow!velocities!(<1!cm!sT1),!resulting!in!maximum!deposition!at!the!marsh!
edge.!Additionally,!tidal!creeks!constrain!water!flow!inside!the!channel!at!elevations!
below!the!marsh!surface.!As!depth!increases,!water!overtops!the!channel!bank,!
resulting!in!an!outward!flow!of!water,!nutrients,!and!sediment!from!the!creek!to!the!
marsh!surface.!!
Along!marshTbay!boundaries,!stunted!vegetation!at!the!edge!is!less!effective!
at!slowing!velocity!(fig!1.2).!Additionally,!waves!generated!in!the!bay!episodically!
!
!
4!
increase!bed!shear!stress!and!SSC!on!the!tidal!flats!bordering!the!marsh.!Waves!also!
contribute!to!lateral!erosion!of!the!marsh!edge!and!vertical!erosion!of!the!marsh!
surface!close!to!the!edge.!Furthermore,!complex!patterns!of!tidal!and!windTdriven!
flow!on!the!flats!and!marsh!generate!uncertainty!about!whether!resuspended!
sediment!on!the!flats!is!carried!onto!the!marsh!platform!or!out!into!the!bay.!This!
research!seeks!to!better!characterize!sediment!availability!and!delivery!to!marshes!
with!open!bay!boundaries,!including!the!wind,!wave,!and!current!conditions!that!
maximize!the!flux!of!sediment!from!the!bay!onto!the!marsh.!!
!
!
Figure(1.1:(Conceptual!model!of!processes!affecting!inorganic!sediment!deposition!on!a!tidal!creek!marsh.!
Direc&onal+ou-low+of++
water,+nutrients+&+sediment+to++
marsh+
Thicker+and+taller+plants+at+the+edge+
Maximum+deposi&on+at+edge+
Water+rises,+eventually++
overtopping+creek+banks+MHHW+
MSL+
MLLW+
Levee+forma&on+
Low+shear+stress+
Decreased+velocity+with+increased+distance+away+from+bank+
Sediment+is+not+remobilized+aEer+ini&al+deposi&on+
Coarser+sediment+&+flocs+deposited+
Finer+sediment+carried+further+away+from+bank+and+deposited+
Increased+SSC+with+
higher+&dal+amplitude+
!
!
5!
!
Figure(1.2:(Conceptual!model!of!processes!affecting!inorganic!sediment!deposition!on!a!marsh!island.!!
(
1.3(Background!
Wind%Waves%
% The!presence!of!windTgenerated!waves!on!tidal!flats!bordering!bayTmarsh!
boundaries!is!the!most!important!difference!affecting!the!sediment!dynamics!of!
these!types!of!marsh!edges!compared!to!tidal!creekTmarsh!edges.!Wind!wave!
formation!within!shallow!bays!relies!on!energy!transfer!from!the!wind!to!the!water!
surface!of!the!bay;!waves!do!not!propagate!into!the!coastal!bays!from!the!ocean.!
Wave!formation!depends!on!wind!characteristics,!such!as!duration,!direction,!and!
velocity,!along!with!water!depth!and!fetch!(Mariotti!et!al.!2010).!Higher!wind!
velocities!and!longer!wind!durations!typically!generate!larger!waves.!Wind!direction!
Wind%waves+
Unconstrained+currents+
Variable+edge+profile+
SSC+
Sediment+deposi;on+on+marsh+
Coarser+sediment+on+;dal+flat+
Finer+sediment+in+marsh+interior+
Stunted+vegeta;on+along+marsh+edge+
Increased+biomass+in+marsh+interior++
BoAom+Resuspension+
Marsh+surface+erosion+on+marsh+edge+
Irregular+edge+erosion+
Traps+sediment+and+slows+flow+velocity+
Wind+
MHHW+
MSL+
MLLW+
Sediment+carried+away+from+marsh+
!
!
6!
determines!fetch,!or!the!unobstructed!distance!over!the!water!that!the!wind!blows.!
Fetch!determines!the!actual!amount!of!energy!that!can!be!transferred!from!the!wind!
to!the!water!surface.!Additionally,!water!depth!directly!controls!maximum!possible!
wave!height.!Thus,!increasing!water!depth,!due!to!tides,!storm!surge,!or!RSLR,!
allows!larger,!higher!energy!waves!to!form.!Furthermore,!depth!indirectly!controls!
wave!height!through!fetch,!because!when!dry!periphery!areas!are!wetted!the!
surface!area!over!which!the!wind!can!blow!increases!(Mariotti!et!al.!2010;!
Fagherazzi!&!Wiberg!2009).!
!
Currents%
Tidal!currents,!which!may!be!enhanced!by!wind!forcing!and!wind!waves,!
transport!sediment!from!the!tidal!flat!to!the!marsh!or!out!into!the!bay,!thus!further!
influencing!entrainment!and!depositional!processes!(Carniello!et!al.!2012).!!The!
trajectory!of!suspended!sediment!in!shallow!lagoon!systems!is!variable.!Factors!
influencing!currents!include!bay!bottom!and!marsh!edge!morphology,!as!well!as!
subtidal!and!intertidal!vegetation.!Although!currents!also!generate!bed!shear!stress,!
waveTinduced!bottom!shear!stress!is!primarily!responsible!for!sediment!
resuspension!over!tidal!flats!(Lawson!et!al.!2007;!Carniello!et!al.!2012).!!!
!
Suspended%Sediment%Concentration%
! !Sediment!is!mobilized!when!the!bottom!shear!stress!imparted!by!
hydrodynamic!forcing!due!to!tidal!currents,!windTinduced!currents,!and!windT
induced!waves,!exceeds!the!critical!shear!stress!for!erosion.!Critical!shear!stress!
!
!
7!
required!for!erosion!depends!upon!sediment!composition!and!degree!of!bed!
consolidation!(Mehta!1988).!Critical!shear!stress!is!positively!correlated!with!grain!
size,!thus!smaller!grains!are!preferentially!mobilized!relative!to!larger!grains,!
although!the!effects!of!cohesion!can!complicate!this!in!muddy!sediment.!Sit!and!clayT
size!sediment!goes!directly!into!suspension!once!mobilized,!therefore!the!threshold!
of!motion!corresponds!to!the!threshold!for!suspension.!Suspended!sediment!
concentration!(SSC)!increases!with!increasing!shear!stress!provided!sediment!is!not!
supply!limited!(Rubin!&!Topping!2001),!and!typically!decreases!with!height!above!
the!sediment!bed,!such!that!nearTbed!concentrations!may!be!2!or!3!orders!of!
magnitude!greater!than!concentrations!near!the!surface!(Mehta!1988).!Additionally,!
Lawson!et!al.!(2007)!found!a!positive!correlation!between!SSC!and!wind!speed!when!
winds!exceeded!8!m!sT1!in!Hog!Island!Bay.!!
! !
Shear%Stress%on%Tidal%Flats%
Internal!resuspension!(Lawson!et!al.!2007)!and!marsh!edge!erosion!(Day!et!
al.!1998;!McLoughlin!et!al.!2014)!contribute!to!SSC!within!the!bays!and!tidal!creeks!
of!the!VCR.!The!amount!of!material!removed!from!edges!and!tidal!flats!is!a!function!
of!the!shear!stress!applied.!Wind!waves!and!currents!(windTdriven!and!tidal)!
determine!shear!stress!distribution!on!tidal!flats!(Fagherazzi!&!Wiberg!2009;!
Carniello!et!al.!2011).!The!combination!of!wave!and!current!stresses!enhances!the!
actual!bed!shear!stress!beyond!the!sum!of!both!factors!(Mariotti!et!al.!2010),!due!to!
the!interaction!between!wave!and!current!boundary!layers!(Carniello!et!al.!2011).!In!
general,!tides!generate!insufficient!bed!shear!stresses!to!resuspend!sediment,!such!
!
!
8!
that!most!resuspension!occurs!during!wind!events!that!produce!relatively!large!
surface!waves,!windTdriven!currents,!and!storm!surge!(Lawson!et!al.!2007).!WaveT
generated!bed!shear!stress!is!a!function!of!water!depth!as!well!as!wave!height!and!
period.!For!given!wave!conditions,!as!water!depth!increases,!waveTgenerated!shear!
stress!decreases.!However,!increasing!water!depth!allows!for!the!formation!of!larger!
waves!in!depthTlimited!systems!like!the!bays!of!the!VCR.!Therefore,!the!relationship!
between!increasing!water!depth!and!bed!shear!stress!is!not!straightforward!
(Fagherazzi!&!Wiberg!2009).!!
Bottom!shear!stresses!are!strongly!influenced!by!the!morphology!of!the!
intertidal!landscape!(Fagherazzi!et!al.!2006;!Defina!et!al.!2007).!Although!wave!
height!and!fetch!increase!with!water!depth,!greater!depths!can!reduce!the!shear!
stress!exerted!on!the!bed!by!waves.!!Fagherazzi!and!Wiberg!(2009)!identified!four!
bottom!shear!stress!regimes!acting!on!tidal!flats!that!vary!as!a!function!of!water!
depth,!wave!height,!and!fetch.!At!tidal!elevations!below!Mean!Lower!Low!Water!
(MLLW),!increased!fetch!and!wave!height!coincide!with!increased!water!depth.!
Since!these!forces!counteract!one!another,!bottom!shear!stress!does!not!change!
significantly.!As!water!rises!from!MLLW!to!Mean!Sea!Level!(MSL)!(i.e.!common!tidal!
flat!elevation!range),!water!depth!reduces!shear!stress!despite!slight!increases!in!
wave!height!and!fetch.!The!greatest!average!shear!stress!is!associated!with!tide!
levels!ranging!from!MSL!to!MHHW!(i.e.!common!tidal!salt!marsh!elevation!range).!
This!is!because!fetch!increases!due!to!marsh!platform!inundation,!and!wave!height!
increases!more!quickly!than!depth.!Finally,!above!MHHW,!wave!height!increases!
!
!
9!
more!slowly!than!water!depth.!Greater!depths!reduce!the!frictional!force!exerted!by!
surface!waves!on!the!bottom,!thus!lowering!shear!stress.!
%
Edge%Erosion%%
Wind!waves!are!the!primary!cause!of!lateral!edge!erosion!along!many!marsh!
shorelines,!including!those!within!the!VCR!(Möller!et!al.!1996,!1999).!Wave!energy!
dissipation!occurs!when!waves!impinge!upon!the!marsh!boundary,!thus!scouring!
and!eroding!the!edge!(Tonelli!et!al.!2010).!Erosion!of!marsh!edges!provides!a!
potentially!significant!source!of!sediment!for!bays!and!marshes!(Mariotti!&!Carr!
2014).!When!previously!intact!sediment!detaches!from!the!edge!due!to!wave!
scouring!it!can!increase!the!amount!of!sediment!in!the!water!column.!Currents!
transport!this!newly!added!sediment!either!back!onto!the!marsh!surface!or!further!
away!to!other!areas!within!the!bay.!!!
Edge!profile!influences!wave!energy!dissipation!along!a!bayTmarsh!boundary.!
For!a!given!tidal!height,!wave!thrust!is!maximum!along!a!vertical!scarp!and!
minimum!along!a!terraced!scarp!(Tonelli!et!al.!2010).!However,!for!a!given!scarp!
thrust!varies!based!on!water!depth.!For!a!vertical!edge!profile,!as!tide!level!
increases,!wave!thrust!increases!to!a!maximum!at!an!elevation!just!below!the!marsh!
platform!height.!For!depths!greater!than!the!platform!height!(i.e.!when!the!marsh!is!
inundated),!wave!thrust!rapidly!decreases!with!increasing!tidal!elevation!until!a!
depth!at!which!the!waves!and!the!bank!do!not!interact!(Tonelli!et!al.!2010).!For!
terraced!scarps,!during!lower!tidal!elevations!most!wave!energy!is!dissipated!on!the!
lower!terrace.!During!tidal!elevations!close!to!the!platform!elevation,!energy!is!
!
!
10!
distributed!upon!both!upper!and!lower!terraces!(Tonelli!et!al.!2010).!Therefore,!at!a!
given!location!along!a!marsh!boundary,!erosion!potential!varies!from!the!bottom!to!
the!top!of!the!edge.!!
!
Aboveground%Marsh%Vegetation%%
Aboveground!marsh!vegetation!dissipates!waves!(Möller!et!al.!1999)!and!
currents,!as!well!as!associated!bed!shear!stresses.!This!allows!for!highly!efficient!
inorganic!sediment!trapping!(Mudd!et!al.!2010),!while!dampening!the!potential!for!
sediment!remobilization.!!The!effectiveness!of!vegetation!at!attenuating!energy!
depends!upon!both!shoot!density,!which!affects!horizontal!friction,!as!well!as!
vegetation!height,!which!influences!the!depth!of!the!boundary!layer!(Möller!2006).!!
! !
Sea%Level%Rise%&%Changing%Waves%
Increased!depth!due!to!RSLR!and!strengthened!winds!will!likely!result!in!
larger!wind!waves.!From!1985!to!2008,!both!mean!and!90th!percentile!wind!speeds!
in!the!North!Atlantic!increased!by!approximately!0.04!m!sT1!each!year!(Young!et!al.!
2011).!Given!the!current!rates,!within!the!next!half!century!both!median!and!90th!
percentile!wind!speed!will!increase!by!2!m!sT1.!Larger!waves!may!increase!the!
amount!of!sediment!resuspended!from!tidal!flats.!On!one!hand,!larger!waves!
generate!greater!bottom!shear!stresses!at!any!given!water!depth.!On!the!other!hand,!
deeper!water!decreases!the!bottom!shear!stress!for!a!given!wave!height!and!period.!
In!either!case,!increased!accretion!due!to!increased!erosion!and!resuspension!will!
only!occur!if!currents!transport!sediment!onto!the!marsh!instead!of!along!the!marsh!
!
!
11!
edge!or!further!out!into!the!bay.!This!has!not!been!accounted!for!in!most!marsh!
models,!which!may!overestimate!surface!accretion!rates!on!marshes!bordering!
shallow!bays.!!!
In!addition,!larger!waves!may!increase!rates!of%lateral!erosion.!Edge!erosion!
elevates!sediment!supply!on!the!tidal!flat,!which!may!subsequently!be!transported!
back!onto!the!marsh!and!increase!surface!accretion.!This!would!create!a!stabilizing!
mechanism!whereby!enhanced!edge!erosion!decreases!the!potential!for!surface!
drowning!(Mariotti!&!Carr!2014).!However,!this!mechanism!relies!on!currents!to!
carry!sediment!to!the!marsh!platform,!which!is!uncertain!given!the!unconstrained!
flow!environment!present!at!marshTbay!boundaries.!
!
1.4(Site(Description(
The!study!site!is!located!along!a!section!of!the!edge!of!Chimney!Pole!Marsh,!a!
marsh!island!bordering!Hog!Island!Bay,!a!shallow,!microtidal!coastal!bay!near!the!
southern!end!of!the!Delmarva!Peninsula!(fig!1.3,1.4).!Hog!Island!Bay!is!part!of!the!
VCR,!a!barrierTlagoonTmarsh!system!extending!over!100!km!along!the!Atlantic!side!
of!the!peninsula.!The!bay!is!approximately!100!km2,!and!about!50%!of!the!bay!is!less!
than!1!m!deep!at!mean!low!tide.!Tides!within!the!bay!are!semidiurnal,!with!a!mean!
tidal!range!of!~1.2!m!(Oertel!2001,!Lawson!et!al.!2007,!Mariotti!&!Fagherazzi!2013).!
Additionally,!RSLR!along!the!Delmarva!coast!is!approximately!4!mm!yrT1!(Zervas!
2001).!!
In!the!VCR,!creeks!input!only!small!amounts!of!sediment!into!the!system.!
Therefore,!most!sediment!processes!occur!via!redistribution!of!sediment!by!
!
!
12!
currents!between!the!shallow!lagoons,!barrier!islands,!and!tidal!salt!marshes!that!
comprise!this!ecosystem!(Mariotti!&!Fagherazzi!2010).!SSC!does!not!exhibit!
periodicity!on!tidal!time!scales,!signaling!nonTperiodic!forcing,!such!as!windTdriven!
waves!(Lawson!et!al.!2007).!Due!to!the!low!population!and!human!development!
both!within!and!near!the!VCR,!sediment!processes!are!minimally!impacted!by!
human!activity.!
The!elevation!of!the!marsh!surface!at!the!study!sites!ranges!from!~!0.4!to!
0.65!m!above!MSL!(McLoughlin!2010).!Surface!elevation!decreases!from!the!marsh!
edge!to!the!marsh!interior,!which!slopes!downward!towards!a!large!tidal!channel!
behind!the!study!site.!Given!its!elevation,!the!study!site!does!not!flood!every!tidal!
cycle!during!neap!tides.!LongTterm!lateral!edge!erosion!rates!range!from!less!than!
0.5!m!yrT1!to!greater!than!2!m!yrT1!(McLoughlin!et!al.!2014).!!On!the!marsh,!Spartina%
alterniflora!biomass!increases!from!the!marsh!edge!to!the!interior.!!Additionally,!
McLoughlin!(2010)!found!that!median!and!mean!grain!sizes!on!Chimney!Pole!marsh!
decrease!from!the!edge!(49.4!μm!and!64.3!μm,!respectively)!to!the!interior!(42.8!μm!
and!55.7!μm).!There!is!a!high!abundance!of!periwinkle!snails!(150T225!per!m2)!and!
large,!interconnected!crab!burrows!in!the!study!area,!which!reduce!sediment!shear!
strength,!thereby!promoting!erosion!of!the!marsh!edge!(McLoughlin!2010).!!
!
!
13!
!
Figure(1.3:(Maps!showing!location!of!Chimney!Pole!Marsh!inside!Hog!Island!Bay,!as!well!as!the!location!of!transects!A!and!B.!!
!
!
14!
!
Figure(1.4:(ZoomedTin!site!map!of!transect!A!and!B!detailing!important!landscape!features.!!
!
!
!
!
15!
1.5(Approach(
For!this!study,!we!established!two!transects!(A!&!B)!that!crossed!variably!
eroding!edges!and!extended!from!the!lagoon!to!the!marsh!interior!(~22!m!long).!
Transect!A!crosses!a!gently!sloped,!slowing!eroding!(0.5!m!yrT1)!edge,!and!transect!B!
crosses!a!quickly!eroding!(1.5!to!2!m!yrT1)!cliff!scarp.!At!both!transects,!the!edge!
orientation!is!northeast!(~30°)!to!southwest!(~210°)!
Current,!wave,!and!turbidity!measurements!were!taken!at!4!monitoring!
stations!(i.e.!lagoon,!tidal!flat,!marsh!edge,!and!marsh!interior)!that!varied!in!
distance!from!the!bayTmarsh!boundary.!Measurements!were!taken!at!either!transect!
A!or!B,!or!at!both!transects,!during!4!separate!deployments!(i.e.!FebTMar!2013,!MayT
Jun!2013,!NovTDec!2013,!and!Mar!2014)!(fig!1.5).!Multiple!deployments!allowed!us!
to!capture!seasonal!trends!in!winds,!hydrodynamics,!and!SSC.!The!first!two!
deployments!focused!primarily!on!transect!A,!whereas!the!last!two!deployments!
focused!on!transect!B.!Simultaneous!recording!at!both!stations!was!limited!by!the!
number!of!instruments!available!for!deployment.!Additionally,!along!both!transects,!
biomass!was!measured!at!3!marsh!stations!(i.e.!marsh!edge,!middle!marsh,!and!
marsh!interior)!and!sediment!characteristics!at!4!stations!(i.e.!the!3!marsh!stations!
and!the!tidal!flat).!!Sediment!deposition!was!also!measured!along!transect!B!at!the!
same!3!marsh!stations.!
!
!
16!
%
Figure(1.5:(Deployment!timeline!detailing!instrument!type!and!location,!as!well!as!other!measurements!that!were!taken.!!!
%
!
!
!
Transect!A:!• ADP:!TF,!ME,!MI!• WG:!TF,!ME!• BM:!ME,!MD,!MI!
2013:&Feb7Mar!!
Transect!A:!• ADP:!TF,!ME,!MI!• WG:!TF,!ME,!MI!• OBS:!ME!!Transect!B:!• WG:!TF,!ME,!MI!
!May7Jun!!
!Nov7Dec!!
Transect!A:!• WG:!TF,!ME!• OBS:!TF!• BM:!ME,!MD,!MI!!Transect!B:!• ADP:!TF,!ME,!MI!• WG:!L,!TF,!ME!(2),!MI!• OBS:!L,!TF,!ME,!MI!• DP:!ME,!MD,!MI!• BM:!ME,!MD,!MI!
Transect!A:!• SA:!TF,!ME,!MD,!MI!!Transect!B:!• ADP:!TF,!ME!• WG:!L,!TF,!ME!• OBS:!L,!TF,!ME!• SA:!TF,!ME,!MD,!MI!• DP:!ME,!MD,!MI!
2014:&Mar!
Legend:&&ADP:!Acoustic!Doppler!Profiler!!BM:!Biomass!Sampling!DP:!Deposition!Plates!L:!Lagoon!MD:!Middle!Marsh!ME:!Marsh!Edge!!
MI:!Marsh!Interior!OBS:!Optical!Backscatter!Sensor!SA:!Sediment!Analysis!TF:!Tidal!Flat!WG:!Wave!Gauge!!
!
!
17!
Chapter(2:(Effect(of(Wind(on(Currents(and(Waves(
(
2.1(Objectives(
( A!main!objective!of!this!study!is:!What!is!the!effect!of!wind!on!wave!
formation!and!current!magnitude!and!direction!on!shallow!tidal!flats!and!bordering!
salt!marshes?!We!compared!wind!speed!and!direction!data!from!nearby!
meteorological!stations!to!current!and!wave!measurements!taken!along!tidal!flat?to?
marsh!transects!during!several!deployments.!This!allowed!us!to!determine!a!
relationship!between!the!variables,!as!well!as!identify!any!seasonal!trends.!In!
developing!these!relationships,!we!also!investigated!the!influence!of!factors!such!as!
marsh!edge!morphology!and!bay!bathymetry!on!current!direction!and!wave!
propagation.!!!
!
2.2(Methods—Data(Collection(and(Analysis(
! Water!depth,!waves!and!currents!were!recorded!at!sites!along!Transect!A!
and!B!(see!fig!1.5)!as!described!below.!The!sampling!locations!on!each!transect!
included!the!tidal!flat,!marsh!edge,!and!marsh!interior!(table!2.1).!Additional!sites!
were!sampled!during!some!but!not!all!deployments.!!
Transect! Station! Acronym! Latitude! Longitude! Elevation!A! Tidal!Flat! TAF$ 37°27'46.73"N$ 75°42'58.44"W$ ?0.45!m!!A! Edge! TAE$ 37°27'46.56"N$ 75°42'57.96"W$ 0.65!m!!A! Interior! TAI$ 37°27'46.32"N$ 75°42'56.88"W$ 0.56!m!!B! Tidal!Flat! TBF$ 37°27'58.62"N$ 75°42'58.26"W$ ?0.5!m!B! Edge! TBE$ 37°27'58.56"N$ 75°42'58.11"W$ 0.55!m!B! Interior! TBI! ! ! 0.40!m!
(Table(2.1:(Latitude,!longitude,!and!elevation!for!tidal!flat,!edge,!and!interior!measuring!stations!at!transects!A!and!B.!Elevations!are!given!relative!to!MSL.!!
!
!
18!
Water&Depth&&&Storm&Surge(
Two!types!of!instruments,!acoustic!Doppler!profilers!(ADPs)!and!wave?tide!
gauges,!recorded!depth!at!15?minute!intervals!during!each!deployment.!Depth!was!
determined!from!pressure!records!that!were!corrected!for!fluctuations!in!
atmospheric!pressure!and!referenced!to!mean!sea!level!(MSL)!datum!recorded!at!
the!Wachapreague,!VA!NOAA!tide!station.!!In!addition,!storm!surge!was!estimated!as!
the!difference!between!predicted!and!observed!tides!recorded!at!the!Wachapreague!
VA!station.!!
&
Currents&
Nortek!AS!Aquadopp©!ADPs!measured!horizontal!and!vertical!velocities!(i.e.!
East,!North,!Up)!every!15?minutes!at!specified!intervals!(e.g.!0.1m!cells)!above!a!
given!blanking!distance.!The!blanking!distance!(e.g.!0.1!or!0.2m)!is!the!distance!
above!the!ADP!sensor!head!below!which!the!instrument!cannot!reliably!record.!!The!
ADPs!also!output!signal!strength,!a!proxy!for!SSC.!As!SSC!increases,!the!strength!of!
the!acoustic!return!signal!also!increases.!!
We!deployed!ADPs!for!3!to!4!weeks!at!different!times!of!the!year!(see!fig!1.5),!
which!allowed!us!to!identify!seasonal!trends.!!During!a!given!deployment,!multiple!
ADPs!recorded!along!one!transect,!providing!simultaneous!current!measurements!
on!the!tidal!flat,!at!the!marsh!edge,!and!in!the!marsh!interior.!We!attached!the!
upward?looking!ADPs!to!metal!frames!and!used!either!stakes!(marsh)!or!dive!
screws!(tidal!flat)!to!secure!the!frames!to!the!ground.!!
!
!
19!
The!data!collected!from!the!instrument!were!analyzed!in!Matlab®.!The!data!
were!filtered!to!remove!false!readings!due!to!the!reflection!of!the!beam!off!the!water!
surface!during!times!of!shallow!water.!Filtering!the!data!by!depth!ensured!that!the!
height!of!the!cells!containing!values!did!not!exceed!the!water!depth!at!a!given!time.!
On!the!marsh,!readings!were!averaged!over!the!whole!current!profile.!On!the!tidal!
flat,!measurements!were!averaged!at!various!elevations!to!analyze!currents!both!
above!and!below!the!marsh!platform!elevation.!!
!
Wind&Waves&
RBR,!Ltd.!wave?tide!gauges!were!deployed!simultaneously!with!the!ADPs!
(see!fig!1.5).!Pressure!readings!from!the!gauges!were!further!processed!with!RBR’s!
Ruskin!software!to!obtain!both!depth!and!wave!statistics,!such!as!significant!wave!
height!and!peak!period.!The!gauges!were!programmed!to!sample!at!either!4!or!6!Hz!
every!15!minutes.!!!!
Multiple!wave?tide!gauges!simultaneously!recorded!waves!along!a!given!
transect,!which!allowed!us!to!resolve!wave!propagation!from!the!bay!to!the!marsh!
interior.!On!the!marsh,!the!gauges!were!attached!to!metal!frames,!which!were!
staked!to!prevent!the!frames!from!moving.!On!the!tidal!flat!and!in!the!bay,!the!
gauges!were!attached!to!10!foot,!0.75!inch?diameter!PVC!pipes.!The!pipes!were!
pushed!approximately!3!feet!into!the!ground!until!the!bottom!of!the!gauge!was!flush!
with!the!bed!surface.!!
!
!
!
!
20!
2.3(Methods—Calculations(
Current6generated&Bottom&Shear&Stress&
! After!the!data!were!processed,!current?generated!bed!shear!stress!were!
calculated!using!the!expression:!
!
where!ρ=1020!kg/m3!is!water!density,!u!is!current!speed!and!Cd!is!the!drag!
coefficient.!The!drag!coefficient!was!estimated!as:!!
!
where!n!is!the!roughness!coefficient!
!
(Hornberger!et!al.!1998;!Lawson!et!al.!2007),!h!is!the!water!depth,!g=9.81!m/s2,!and!
D84!is!the!84th!percentile!of!the!grain!size!distribution.!!
!
Wave6generated&Bottom&Shear&Stress&
Wave?induced!bottom!orbital!velocity!was!calculated!using!linear!wave!
theory:!
!
and!wave?generated!bed!shear!stress!was!estimated!as:!
!!!!!!!!!!!!!! !
(Eq.!2.4)!
(Eq.!2.5)!
(Eq.!2.1)!
(Eq.!2.2)!
(Eq.!2.3)!
!
!
21!
where!
!
Hs!is!significant!wave!height,!T!is!wave!period,!k!is!wave!number!(2π/L),!L!is!wave!
length,!fw!is!the!friction!factor,!and!kb=3D84&is!the!roughness!length!scale!of!the!bed!
(Fredsoe!&!Deigaard!1992).!The!wave!number!k!is!calculated!using!the!dispersion!
equation!derived!from!linear!wave!theory!
!
where!σ!=!2π/T.!
(
2.4(Results(
Water&Depth&&&Storm&Surge&
Depth!data!provide!an!indication!of!the!elevations!of!sampling!locations!
relative!to!MSL!(tbl!2.1).!Depth!measurements!indicate!that!TBE!(0.55!m)!is!lower!in!
elevation!than!the!TAE!(0.65!m),!and!that!the!marsh!interior!(0.4!m!and!0.56!m)!is!
lower!than!the!marsh!edge!at!both!sites!(fig!2.1,!2.2).!!As!a!result,!site!B!floods!more!
frequently!that!site!A.!When!the!marsh!is!flooded!the!water!is!deeper!in!the!interior!
than!along!the!edge,!and!the!interior!remains!inundated!with!water!for!longer!
periods!of!time!(tbl!2.4).!!
A!comparison!of!measured!tides!to!predicted!tides!recorded!at!the!
Wachapreague,!VA!NOAA!station!provides!evidence!of!storm!surge!in!the!coastal!
bays!(tbl!2.2).!The!highest!mean!surge!occurred!during!the!early!spring!(0.2291!m!
and!0.2426m),!whereas!the!mean!surge!in!the!summertime!was!much!lower!(0.0933!
(Eq.!2.6)!
(Eq.!2.7)!
!
!
22!
m).!This!is!unsurprising!given!that!strong!winds!(>8!m!s?1)!from!the!north!that!force!
storm!surge!(Fagherazzi!et!al!2010;!Mariotti!et!al.!2010)!are!more!prevalent!in!the!
winter!(fig!2.3;!fig!2.18).!!!
!
!
Figure(2.1:(Water!depth!(m)!relative!to!MSL(m)!recorded!at!transect!B!during!November!and!!!December!2013;!the!line!labeled!“wach”!shows!the!measure!tide!at!the!nearby!NOAA!Wachapreague!tide!gauge.!!
320 325 330 335 340 345 350−1
−0.5
0
0.5
1
1.5
Day of 2013
Dep
th [m
]
wachbaytidal flatedgemid−edgeinterior
!
!
23!
(
Figure(2.2:(Water!depth!(m)!relative!to!MSL!recorded!at!transect!A!during!May!and!June!2013;!the!line!labeled!“wach”!shows!the!measure!tide!at!the!nearby!NOAA!Wachapreague!tide!gauge.!!
Deployment( HTm>(HTp( Average(Surge(Feb?Mar!2013! 43.6%! 0.2291!m!!May?Jun!2013! 46.2%! 0.0933!m!!Nov?Dec!2013! 73.5%! 0.1642!m!!Mar!2014! 77.3%! 0.2426!m!!
&&&&&&&&&&&&&Table(2.2:(Storm!surge!calculated!as!the!difference!between!measured!high!tide!(HTm)!and!predicted!high!tide!(HTp).!HTm>HTp!indicates!the!number!of!times!that!measured!high!tide!exceeded!the!predicted!high!tide,!relative!to!the!total!number!of!high!tides!in!the!deployment.!&
&
140 145 150 155 160 165 170 175 180−1.5
−1
−0.5
0
0.5
1
1.5
Day of 2013
Dept
h [m
]
Wachtidal flatedgeinterior
!
!
24!
!
Figure(2.3:(Top:!wind!speed!(m/s)!recorded!at!the!South!Bay!station!and!plotted!as!the!direction!towards!which!the!wind!is!blowing.!Bottom:!Depth!(m)!relative!to!MSL!of!predicted!and!observed!tides!recorded!at!the!Wachapreague,!VA!NOAA!station!during!March!2014.!!&
Currents&(Transect&A)&
In!the!Virginia!coastal!bays,!southerly!winds!are!more!common!relative!to!
northerly!winds,!particularly!during!the!summertime.!Winds!influence!the!
magnitude!and!direction!of!tidal!currents.!Figure!2.4!compares!wind!patterns!to!
mean!current!magnitude!and!direction!averaged!over!the!entire!water!column!at!
TAF.!Southerly!winds!correspond!with!an!alternating!northward!flood,!southward!
ebb!current!pattern.!Conversely,!in!the!presence!of!stronger!northerly!winds,!
60 65 70 75 80 85 90−20
−15
−10
−5
0
5
10
Win
d Sp
eed
[m/s
]
60 65 70 75 80 85 90−1.5
−1
−0.5
0
0.5
1
1.5
Dep
th
Day of 2014
Pred Obs
!
!
25!
currents!flow!towards!the!south,!regardless!of!tidal!phase!though!with!tidally!
varying!speeds.!Average!current!speeds!during!times!of!weaker!southerly!winds!
were!less!than!half!(<5!cm/s)!the!speeds!during!periods!of!stronger!northerly!winds!
(>10!cm/s).!As!discussed!below,!current!speeds!also!increased!during!spring!tide.!!!
Current!magnitude!and!direction!recorded!on!TAF!at!water!elevations!
exceeding!the!marsh!elevation,!as!well!as!currents!recorded!at!TAE!and!TAI,!are!
presented!in!figure!2.5.!On!the!tidal!flat,!tides!flowed!towards!the!northeast!during!
flood!tide,!and!towards!the!southwest!during!ebb!tide!(fig!2.5a,!b).!The!dominant!
axis!of!water!movement!(NE?SW)!paralleled!the!marsh!edge!(NE?SW).!On!the!marsh!
platform,!water!flooded!the!marsh!from!Hog!Island!Bay!and!ebbed!towards!the!large!
tidal!creek!behind!the!site!(fig!2.5c,d,e,f;!see!fig!1.4).!It!is!important!to!note!that!data!
collected!from!the!marsh!were!limited!by!infrequent!flooding!during!the!
deployment,!as!well!as!the!ADP!blanking!distance.!The!marsh!currents!displayed!in!
figure!2.5!occurred!over!multiple!tidal!cycles!during!spring!tide.!
!
!
26!
!
Figure(2.4:(From!top!to!bottom:!wind!speed!(m/s)!recorded!at!the!South!Bay!station!and!plotted!as!the!direction!towards!which!the!wind!is!blowing,!depth!(m)!relative!to!MSL,!and!current!magnitude!(cm/s)!plotted!as!the!direction!towards!which!the!water!is!flowing.!Currents!were!averaged!over!the!entire!height!of!the!water!column!and!recorded!at!TAF!during!February?March!2013.!!!!!!!!!!!!!!!
45.5 46 46.5 47 47.5 48 48.5−10
−5
0
5
10
Win
d Sp
eed
[m/s
]
45.5 46 46.5 47 47.5 48 48.5−1
−0.5
0
0.5
1
Wat
er E
lev
[m]
45.5 46 46.5 47 47.5 48 48.5−20
−10
0
10
20
Cur
rent
Spe
ed [c
m/s
]
Day of 2013
!
!
27!
!
!
!
!!!!!!!!!!!!!!!!!!!!!!!!!! !!
! !!
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
5%
10%
15%
WEST EAST
SOUTH
NORTH
0 − 2
2 − 4
>=4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
10%
20%
30%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 2
2 − 4
4 − 6
30%
60%
90%
120%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 22 − 4 > 4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 2
2 − 4
4 − 6
20%
40%
60%
80%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
10%
20%
30%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 2
2 − 4
4 − 6
30%
60%
90%
120%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
30%
60%
90%
120%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 22 − 4 > 4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 2
2 − 4
4 − 6
20%
40%
60%
80%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
20%
40%
60%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
5%
10%
15%
WEST EAST
SOUTH
NORTH
0 − 55 − 10> 10
A! B!
C! D!
E! F!
G! Figure(2.5:(Current!speed!(cm/s)!and!direction!(degrees)!recorded!at!transect!A!during!May?June!2013!at:!A)!TAF!during!flood!tide!(ebb!and!flood!currents!were!measured!at!water!elevations!exceeding!the!marsh!elevation);!B)!TAF!during!ebb!tide;!C)!TAE!during!flood!tide;!D)!TAE!during!ebb!tide;!E)!TAI!during!flood!tide;!and!F)!TAI!during!ebb!tide.!Current!roses!show!the!direction!the!water!is!moving!towards.!G)!Wind!speed!(m/s)!and!direction!(degrees)!recorded!in!South!Bay!during!the!same!time!period.!Wind!rose!shows!the!direction!the!wind!is!blowing!from.!!
!
!
28!
Currents&(Transect&B)&
At!TBF,!currents!primarily!flowed!towards!the!southwest,!parallel!to!the!
orientation!of!the!marsh!edge!(NE?SW),!when!measurements!were!averaged!over!
the!entire!water!column!(fig!2.6).!The!southward!flow!was!forced!by!prevailing!
winds!from!the!north!during!the!March!2014!deployment.!!
Figure!2.7!shows!current!patterns!at!transect!B!on!the!marsh!surface.!Water!
floods!the!marsh!edge!from!the!marsh!interior!and!from!the!large!embayment!north!
of!site!B!(fig!2.7c).!Water!ebbs!off!the!marsh!edge!into!Hog!Island!Bay!as!well!as!
southward!towards!site!A!(fig!2.7d).!In!the!marsh!interior,!water!floods!from!Hog!
Island!Bay!and!ebbs!towards!the!small!tidal!creek!behind!site!B!(fig!2.7e,f).!The!
dominant!south?southeast!flow!direction!in!the!interior!was!similar!to!the!current!
pattern!recorded!at!site!A,!but!also!coincided!with!strong!winds!from!the!north?
northwest!during!November!and!December!2013.!!!
!
!
!
!
29!
!
Figure(2.6:(From!top!to!bottom:!wind!speed!(m/s)!recorded!at!the!South!Bay!station!and!plotted!as!the!direction!towards!which!the!wind!is!blowing,!current!magnitude!(cm/s)!plotted!as!the!direction!towards!which!the!water!is!flowing,!and!depth!(m)!relative!to!MSL.!Currents!were!averaged!over!the!entire!height!of!the!water!column!and!recorded!at!TBF!during!March!2014.!!!
!!!!!!!!!!!
60 65 70 75 80 85−15
−10
−5
0
5
10
wnd
spee
d [m
/s]
60 65 70 75 80 85−6
−4
−2
0
2
4
curr
spee
d [c
m/s
]
60 65 70 75 80 85−1
−0.5
0
0.5
1
1.5
dept
h [m
]
Day of 2014
!
!
30!
(
(
(((((((((((( (((
&
&
&
&
&
&
10%
20%
30%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 22 − 4 > 4
10%
20%
30%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 22 − 4 > 4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 55 − 10> 10
C! D!
A! B!
E!Figure(2.7:(Current!speed!(cm/s)!and!direction!(degrees)!recorded!during!November?December!2013!at:!A)!TBE!during!flood!tide;!B)!TBE!during!ebb!tide;!C)!TBI!during!flood!tide;!and!D)!TBI!during!ebb!tide.!Current!roses!show!the!direction!the!water!is!moving!towards.!E)!Wind!speed!(m/s)!and!direction!(degrees)!recorded!in!South!Bay!during!the!same!time!period.!Wind!rose!shows!the!direction!the!wind!is!blowing!from.!!
!
!
31!
Effect&of&Edge&Morphology&on&Currents&
& The!marsh!edge!is!a!morphological!influence!on!flow.!At!TAF,!when!water!
depth!was!both!above!(2.8a)!and!below!the!marsh!elevation!(2.8b),!currents!
primarily!flowed!towards!the!northeast!and!southwest,!which!parallels!the!
orientation!of!the!edge.!Although!the!variability!in!flow!direction!increased!at!water!
depths!higher!than!the!marsh!elevation,!it!was!not!as!remarkable!as!at!TBF.!!When!
water!depth!was!below!the!marsh!elevation!at!TBF,!currents!almost!exclusively!
flowed!towards!the!southwest!(2.8d),!which!also!parallels!the!orientation!of!the!
edge.!Little!northward!flow!was!recorded!due!to!the!prevalence!of!northerly!winds.!
When!depth!exceeded!the!marsh!elevation!at!TBF,!water!either!moved!onto!the!
marsh!or!further!out!into!the!bay!as!unconstrained!flow!(2.8e).!!
!
!
!
!
!
!
‘!
!
!
!
!
32!
!
!
((
Figure(2.8:(Current!speed!(cm/s)!and!direction!(degrees)!recorded!at:!!A!&!D)!water!elevations!below!the!marsh!surface!elevation!at!TAF!and!TBF,!respectively;!and!B!&!E)!water!elevations!exceeding!the!marsh!surface!elevation!at!TAF!and!TBF,!respectively.!C)!Picture!of!edge!at!transect!A.!F)!Picture!of!edge!at!transect!B.!Currents!at!TAF!were!recorded!during!May?June!2013!and!currents!at!TBF!were!recorded!during!March!2014.!!
(
Wind&Waves&(Transects&A&&&B)&
Figure!2.9!shows!significant!wave!height!separated!by!wind!speed!and!
direction.!Westerly!winds!(180°?!360°)!blowing!across!Hog!Island!Bay!produce!the!
15%
30%
45%
WEST EAST
SOUTH
NORTH
0 − 2
2 − 4
>=4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 2
2 − 4
>=4
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
5%
10%
15%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
15%
30%
45%
WEST EAST
SOUTH
NORTH
0 − 2
2 − 4
>=4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
15%
30%
45%
WEST EAST
SOUTH
NORTH
0 − 2
2 − 4
>=4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 2
2 − 4
>=4
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
5%
10%
15%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
15%
30%
45%
WEST EAST
SOUTH
NORTH
0 − 2
2 − 4
>=4
5%
10%
15%
20%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 2
2 − 4
>=4
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 22 − 4> 4
A!
B!
C!
E!
D!
F!
!
!
33!
largest!waves,!because!the!fetch!generated!is!sufficient!for!wave!formation!(fig!2.9).!
On!the!other!hand,!easterly!winds!(<180°)!from!the!Atlantic!blow!across!barrier!
islands!(e.g.!Hog!Island)!and!Chimney!Pole,!thus!inhibiting!wave!formation!due!to!
insufficient!fetch,!particularly!for!sites!bordering!the!marsh.!In!addition!to!direction,!
high!wind!speeds!(>!8!m!s?1)!force!larger!waves!relative!to!lower!wind!speeds!(<!8!m!
s?1).!Mean!wave!heights!for!each!wind!direction!group!were!up!to!3.2!times!higher!
under!high!wind!speed!conditions!compared!to!low!wind!speed!conditions.!At!
Chimney!Pole,!winds!blowing!from!the!west?northwest!(~295°)!(i.e.!the!direction!of!
longest!fetch)!at!high!wind!speeds!generated!the!highest!waves!(median=0.25!m)!
(fig!2.9).!!
Figure!2.10!also!illustrates!the!influence!of!wind!direction!and!wind!speed!on!
wave!height!on!the!tidal!flat.!!When!winds!blew!across!Hog!Island!Bay!at!high!speeds!
(>!8!m!s?1)!the!largest!waves!formed,!which!occurred!on!days!328!and!332.!
However,!when!westerly!winds!coincided!with!low!wind!speeds,!either!small!or!no!
waves!formed,!which!occurred!on!day!337.!!!
Figure!2.11!shows!wave!transformation!at!transect!B!between!the!bay!(~15!
m!offshore!of!the!marsh!edge)!and!marsh!interior.!As!waves!propagated!from!the!
bay!up!onto!the!tidal!flat,!wave!height!increased!by!33%!(fig.!2.11).!Subsequently,!as!
the!waves!crossed!the!marsh!edge!their!height!rapidly!diminished.!Wave!height!
recorded!in!the!bay!was!reduced!by!67,!78,!and!83%!at!the!marsh!edge,!middle!and!
interior,!respectively.!!
Wave!heights!at!the!transect!B!Bay!(TBB)!and!TBF!are!more!similar!to!each!
other!than!to!waves!at!TAF!(fig.!2.12).!Waves!at!TBB!have!a!96%!correlation!with!
!
!
34!
waves!at!TBF!and!an!85%!correlation!with!waves!at!TAF.!Waves!at!TBF!have!a!91%!
correlation!with!waves!at!TAF.!Waves!are!33%!larger!at!TBF!than!at!TBB,!and!are!
6%!larger!at!TBF!compared!to!TAF.!However,!slightly!higher!waves!at!TBF!than!TAF!
are!likely!attributable!to!deeper!depths!due!to!the!instrument’s!location!at!a!lower!
elevation.!!
!
!
Figure(2.9:(Significant!wave!height!compared!to!wind!direction!for!low!(left;!<8!m!s?1)!and!high!(right;!>8!m!s?1)!wind!speeds.!Blue!shading!indicates!westerly!winds!blowing!across!Hog!Island!Bay.!Data!were!recorded!in!February?March!2013!at!TAF.!Wind!speeds!did!not!exceed!8!m!s?1!for!the!25°,!160°,!and!205°!wind!direction!groups,!therefore!there!are!no!data.!!
!
!
!
35!
!
Figure(2.10:(From!top!to!bottom:!wind!direction!(degrees)!and!wind!speed!(m/s)!recorded!in!South!Bay;!water!depth!(m);!and!significant!wave!height!(m)!recorded!at!TBF!during!November?December!2013.!!!!
320 325 330 335 340 345 3500
100
200
300W
ind
Dir
(deg
)
320 325 330 335 340 345 3500
5
10
15
Wnd
Spd
[m/s
]
320 325 330 335 340 345 3500
0.5
1
1.5
2
Wat
erE
lev
[m]
320 325 330 335 340 345 3500
0.2
0.4
0.6
Wav
eHei
ght [
m]
Day of 2013
!
!
36!
!
Figure(2.11:(Average!growth!or!reduction!(%)!in!significant!wave!height!as!waves!propagated!from!the!bay!to!the!marsh!interior,!shown!as!a!percentage!of!the!initial!height!recorded!at!TBB.!Data!were!recorded!during!November?December!2013!at!transect!B.!!!
Tidal Flat On Edge Middle Interior−100
−80
−60
−40
−20
0
20
40
Red
uctio
n(−)
or G
row
th(+
) of W
ave
Hei
ght (
%)
!
!
37!
!
Figure(2.12:(Top:!Depth!(m)!recorded!at!TBB,!TBF,!and!TAF.!Bottom:!Significant!wave!height!(m)!recorded!at!the!same!stations.!Data!were!recorded!during!the!November?December!2013!deployment.!!
!!
Shear&Stress&Regimes&
Waves!account!for!the!largest!proportion!of!total!bed!shear!stress!(fig!2.13,!
2.14).!During!large!storms,!wave?generated!bed!shear!stress!on!the!tidal!flat!was!2!
orders!of!magnitude!larger!than!current?induced!bed!shear!stress.!Current!shear!
stress!on!the!tidal!flat!increased!as!tidal!range!increased!(fig!2.16),!such!that!the!
highest!shear!stress!occurred!during!spring!tide!(fig!2.13).!!
On!the!marsh,!mean!wave?induced!bed!shear!stress!is!17%!higher!at!the!edge!
than!the!interior.!Wave!and!current!bed!shear!stress!on!the!marsh!never!exceeded!
320 325 330 335 340 345 350−0.5
0
0.5
1
1.5
2
2.5
Dept
h (m
)
B BayB TFA TF
320 325 330 335 340 345 3500
0.1
0.2
0.3
0.4
0.5
Sign
ifican
t Wav
e He
ight
(m)
Day of 2013
!
!
38!
0.35!Pa!and!0.005!Pa,!respectively.!Total!shear!stress!on!the!marsh!only!exceeded!
0.07!Pa,!the!critical!threshold!for!suspension,!4.9%!of!the!time!at!TBE!and!3.6%!of!
the!time!at!TBI!during!November!and!December!2013!(fig!2.15).!On!the!tidal!flat,!
total!shear!stress!was!greater!than!0.07!Pa!for!27%!of!the!time.!!
Figure!2.17!shows!total!shear!stress!(waves!+!currents)!on!TBF!as!a!function!
of!depth!and!wind!speed!for!times!when!the!wind!blew!from!a!west?northwest!
direction!(i.e.!the!direction!of!longest!fetch).!When!wind!speeds!are!less!than!8!m!s?1,!
total!bottom!shear!stress!does!not!differ!significantly!among!depth!groups!due!to!
little!wave!formation.!For!every!depth!group,!median!total!shear!stress!under!low!
wind!speed!conditions!(range=0?0.06!Pa)!was!lower!than!under!high!wind!speed!
conditions!(range=0.09?0.35!Pa).!When!wind!speed!exceeded!8!m!s?1,!maximum!
shear!stresses!occurred!at!water!elevations!just!below!MHHW!(~0.7!m),!above!
which!shear!stress!declined!with!increasing!depth.!A!wind!threshold!for!significant!
wave!generation!of!8!m!s?1!was!a!previously!determined!value!from!Lawson!et!al.!
(2007).!
!
!
39!
!
Figure(2.13:(From!top!to!bottom:!depth!(m),!current!shear!stress!(Pa),!wave!shear!stress!(Pa),!and!total!shear!stress!(Pa)!generated!by!both!currents!and!waves!recorded!at!TBF,!TBE,!and!TBI!during!Nov?Dec!2013.!!
!
320 325 330 335 340 345 3500
0.5
1
1.5
2
Dep
th [m
]
Tidal FlatEdgeInterior
320 325 330 335 340 3450
0.005
0.01
0.015
0.02
Cur
r She
ar S
tress
[Pa]
320 325 330 335 340 3450
0.2
0.4
0.6
Wav
e S
hear
Stre
ss [P
a]
320 325 330 335 340 3450
0.2
0.4
0.6
Tota
l She
ar S
tress
[Pa]
Day of 2013
!
!
40!
!
Figure(2.14:(Depth!(m),!significant!wave!height!(m),!and!wave!shear!stress!(Pa)!recorded!in!March!2014!at!TBF!and!TBE.!Note:!the!instrument!located!at!TBE!during!this!deployment!was!closer!to!the!edge!than!during!the!Nov?Dec!2013!deployment!(2.13).!!
!((((((
60 65 70 75 80 85 900
0.5
1
1.5
2
Dept
h [m
]
Tidal Flat Edge
60 65 70 75 80 85 900
0.1
0.2
0.3
0.4
0.5
Sign
ifican
t Wav
e He
ight
[m]
60 65 70 75 80 85 900
0.1
0.2
0.3
0.4
0.5
Wav
e Sh
ear S
tress
[Pa]
Day of 2014
!
!
41!
(Figure(2.15:(Cumulative!distribution!of!total!shear!stress!at!TBF,!TBE,!and!TBI!during!November?December!2013.(!!
!
&
Figure(2.16:(Peak!current!shear!stress!(Pa)!during!each!tidal!cycle!compared!to!tidal!range,!calculated!as!the!difference!between!high!and!low!tide.!Data!were!recorded!at!TBF!during!November?December!2013.!!!
0 0.005 0.01 0.015 0.02 0.025
0.8
1
1.2
1.4
1.6
1.8
2
2.2
Current Shear Stress [Pa]
Tida
l Ran
ge [m
]
y = 56*x + 0.72
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.50
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Total Shear Stress [Pa]
Cum
ulat
ive
Dis
tribu
tion
0 0.05 0.1 0.15 0.2 0.250
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Total Shear Stress [Pa]
Cum
ulat
ive
Dis
tribu
tion
0 0.05 0.1 0.15 0.2 0.250
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Total Shear Stress [Pa]
Cum
ulat
ive
Dis
tribu
tion
!
!
42!
&
Figure(2.17:(Total!shear!stress!(Pa)!as!a!function!of!water!depth!(m)!at!times!when!wind!blew!across!the!bay!from!a!W?NW!direction!(240?305!degrees).!Data!are!separated!into!low!(<8!m/s;!white!boxes)!and!high!(>8!m/s,!blue!boxes)!wind!speed!groups.!Data!were!recorded!at!TBF!in!November?December!2013.!
&
Seasonal&Variations&in&Wind&&&Waves!
Wind!speed!and!direction!displayed!seasonality!in!the!study!area.!From!late!
fall!to!early!spring,!northerly!winds!prevailed!(2.18!a,!c,!d).!Northerly!winds!during!
winter!months!were!typically!stronger!than!the!southerly!winds!that!prevailed!
during!the!early!summer!(2.18b).!!Wind!speeds!exceeded!8!m!s?1!only!5%!of!the!time!
during!the!May?June!2013!deployment!compared!to!12%,!11%,!and!31%!of!the!time!
during!the!February?March!2013,!November?December!2013,!and!March!2014!
!
!
43!
deployments,!respectively.!Although!50th!percentile!wave!heights!did!not!vary!much!
among!different!seasons,!95th!and!98th!percentile!wave!heights!in!the!winter!were!
up!to!12!cm!higher!than!summer!wave!heights!(tbl!2.3).!!
!
!
!(Figure(2.18:!Wind!Direction!recorded!in!South!Bay!during!A)!February?!March!2013;!B)!May?June!2013;!C)!November?December!2013;!and!D)!March!2014.!!
&
&
Deployment( 50th! 75th! 95th! 98th!Feb?Mar!2013! 0.0585! 0.1118! 0.2456! 0.3048!May?Jun!2013! 0.0303! 0.0737! 0.1513! 0.1936!Nov?Dec!2013! 0.0297! 0.0890! 0.2263! 0.3208!Mar!2014! 0.0301! 0.0729! 0.1900! 0.2666!
(Table( 2.3:( 50th,! 75th,! 95th,! and! 98th! percentile! significant! wave! heights! (m)! given! for! all! 4!deployments.!!!!
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 5
5 − 10
>=10
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 5
5 − 10
>=10
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 5
5 − 10
>=10
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 5
5 − 10
>=10
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 5
5 − 10
>=10
5%
10%
15%
WEST EAST
SOUTH
NORTH
0 − 5
5 − 10
>=10
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 55 − 10> 10
5%
10%
15%
WEST EAST
SOUTH
NORTH
0 − 55 − 10> 10
5%
10%
15%
WEST EAST
SOUTH
NORTH
0 − 55 − 10> 10
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 55 − 10> 10
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 5
5 − 10
>=10
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 5
5 − 10
>=10
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 5
5 − 10
>=10
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 5
5 − 10
>=10
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 5
5 − 10
>=10
5%
10%
15%
WEST EAST
SOUTH
NORTH
0 − 5
5 − 10
>=10
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 55 − 10> 10
5%
10%
15%
WEST EAST
SOUTH
NORTH
0 − 55 − 10> 10
2%
4%
6%
8%
WEST EAST
SOUTH
NORTH
0 − 55 − 10> 10
A! B!
C! D!
!
!
44!
! Site!A! Site!B!TAF( TAE( TAI( TBB( TBF( TBE( TBI(
Edge(erosion(rate(
<0.5!m!yr?1! 1.5?2!m!yr?1!
Scarp(slope( low! high!Depth( ?0.5! 0.65! 0.56! ! ?0.5! 0.55! 0.4!Est.(inundation(Freq((days/mo)(
25.5! 2.7! 4.2! 30! 25.5! 5.1! 6.9!
Flood(curr.(dir.(when(marsh(is(flooded(
Along!edge!(NE)!
On?!marsh!(SE)!
On?marsh!(E)!
X! None!(uncon?strained)!
On!&!off?marsh!(SE,!W)!
On?marsh!(E,!SE)!
Ebb(curr.(dir.(when(marsh(is(flooded(
Along!edge!(SW)!
On?!marsh!(SE)!
On?marsh!(ESE)!
X! None!(uncon?strained)!
On!&!off?marsh!(SE,!W)!
On?marsh!(SE)!
90th(Percentile(Hs((m)((MayYJun(2013)(
0.1331! 0.0007! 0.0007! X! 0.1690! 0.0247! 0.0267!
90th(Percentile(Hs((m)((NovYDec(2013)(
0.1832! 0.0017! X! 0.1333! 0.1702! 0.0215! 0.0122!
90th(Percentile(τwav((Pa)(((MayYJun(2103)(
0.0947! 0.0007! 0.0004! X! 0.1164! 0.0210! 0.0135!
90th(Percentile(τwav((Pa)((NovYDec(2013)(
0.1199! 0.0018! X! 0.1489! 0.1533! 0.0058! 0.0099!
(Table(2.4:(Summary!of!key!findings!and!results.!X!indicates!no!data!available.!!
!
2.5(Discussion(
Water&Depth&&&Storm&Surge&
Marsh!surface!topography!strongly!influences!the!frequency!and!duration!of!
marsh!flooding!(Cahoon!&!Reed!1995).!Deeper!water!and!prolonged!inundation!
occurred!at!site!B!due!to!its!lower!elevation!relative!to!site!A.!Given!this,!accretion!
rates!at!site!B!may!be!higher!than!at!site!A.!!!
Storm!surge!strongly!affects!water!level!in!the!Virginia!coastal!bays!(Mariotti!
et!al.!2010).!Evidence!of!storm!surge!in!Hog!Island!Bay!was!found!during!each!
!
!
45!
season,!but!was!highest!during!the!late!winter!to!early!spring.!Storm!surge!enhances!
the!potential!for!sediment!delivery!to!open!boundary!marshes!due!to!prolonged!
inundation.!This!is!particularly!true!when!storm!surge!coincides!with!a!spring!tide!
(Stumpf!1983).!!
Storm!surge!allows!for!the!formation!of!larger!waves,!which!generate!greater!
bottom!shear!stresses!for!any!given!depth.!Our!data!did!not!capture!larger!waves!
during!storm!surge!events,!possibly!due!to!unfavorable!wind!conditions.!For!
example,!strong!winds!from!the!northeast!produce!the!largest!storm!surge!in!the!
Virginia!coastal!bays!(Mariotti!et!al.!2010),!but!generate!little!wave!fetch!at!our!site.!
As!discussed!below,!storm!surge!coincided!with!decreased!wave?induced!bed!shear!
stress!on!the!tidal!flat!and!increased!bed!shear!stress!at!the!marsh!edge.!!
There!is!a!positive!correlation!between!current!speed!and!tidal!range!
(Fagherazzi!et!al.!2013).!The!tidal!prism,!the!amount!of!water!that!enters!and!exits!
the!lagoon!during!a!tidal!cycle,!can!be!approximated!as!the!product!of!tidal!range!
and!the!area!of!the!bay!flooded!by!the!tide.!Given!that!storm!surge!increases!flooded!
area!and!therefore!tidal!prism,!storm!surge!likely!increases!current!magnitude.!!
&
Currents&(Transect&A)&
When!southerly!winds!are!present,!there!is!an!alternating!northward!flood,!
southward!ebb!current!pattern!at!TAF!and!TBF.!Southerly!winds!likely!help!push!
flood!tides!northward,!whereas!tidal!slope!likely!influences!the!southward!ebb!tide.!
On!the!other!hand,!the!southward!flood!and!ebb!current!pattern!that!exists!in!the!
presence!of!stronger!northerly!winds!is!attributable!to!wind!forcing.!!
!
!
46!
!The!transport!of!water!between!the!marsh!and!the!lagoon!occurs!as!a!
shallow!sheet!flow!in!the!absence!of!tidal!creeks!(French!et!al.!1995;!Temmerman!et!
al.!2005).!On!the!marsh,!water!flows!from!the!bay!towards!the!large!tidal!creek!
during!flood!and!ebb!tide.!Faster!draining!of!the!large!tidal!creek!behind!site!A!could!
create!a!water!surface!slope!in!the!direction!of!the!creek.!!Furthermore,!behind!TAI!
the!surface!slopes!sharply!downward!towards!the!creek!(McLoughlin!2010),!which!
may!increase!current!magnitude!in!that!direction.!The!large!creek!is!also!present!
behind!site!B,!but!it!is!further!away!and!therefore!less!influential.!!
!
Currents&(Transect&B)&
Dominant!flood!and!ebb!currents!moved!along!the!edge!towards!the!
southwest!at!TBF!when!measurements!were!averaged!over!the!entire!water!column!
for!the!March!2014!deployment.!This!is!likely!due!to!prevailing!winds!from!the!
north!during!that!time!period,!which!pushed!currents!southward.!We!recorded!a!
northward!flood,!southward!ebb!pattern!during!a!few!instances!when!southerly!
winds!were!present,!which!agrees!with!the!current!pattern!recorded!at!TAF.!!!
At!the!marsh!edge,!water!moves!from!the!marsh!interior!towards!Hog!Island!
Bay.!This!may!be!influenced!by!a!faster!response!of!the!bay!to!ebbing!tide!relative!to!
the!marsh!interior,!causing!the!setup!of!a!tidal!slope.!Water!also!moves!from!the!
large!embayment!north!of!site!B!(see!fig!1.4)!southward!towards!site!A.!The!
irregular!edge!morphology!likely!influences!the!variable!current!patterns!at!TBE.!In!
the!marsh!interior,!flood!and!ebb!tides!move!towards!the!small!tidal!creek!behind!
the!site!(see!fig!1.4).!Faster!draining!of!the!small!creek,!as!well!as!the!steep!
!
!
47!
downward!slope!of!the!marsh!surface!behind!TBI,!likely!force!currents!towards!that!
direction.!Furthermore,!the!prevalence!of!winds!from!the!north?northwest!during!
November!and!December!2013!likely!helped!push!currents!on!the!marsh!towards!
the!south?southeast.!!
!
Effect&of&Edge&Morphology&on&Currents&
Edge!profile!acts!as!a!morphological!influence!on!current!direction.!The!edge!
at!transect!A!is!relatively!straight,!whereas!the!transect!B!edge!is!jagged,!consisting!
of!wave!gullies!and!embayments.!Our!results!indicate!that!at!elevations!below!the!
marsh!platform!height,!the!edge!steered!currents!along!the!marsh!boundary!at!both!
transects.!At!elevations!above!the!marsh!platform,!the!edge!had!little!to!no!effect!on!
current!direction!and!sediment!transport.!Unconstrained!flow!at!elevations!above!
the!marsh!platform!may!facilitate!the!transport!of!the!material!that!is!in!the!water!
column!onto!the!marsh.!Furthermore,!the!high!variability!in!current!direction!at!
water!depths!greater!than!the!marsh!platform!height!may!be!influenced!by!slack!
water!at!high!tide.!!!
!
Sediment&Advection&onto&the&Marsh&
Sediment!deposition!on!the!marsh!platform!relies!on!currents!to!transport!
sediment!across!the!bay?marsh!boundary.!Overall,!the!data!reveal!that!currents!do!
transport!sediment!from!the!bay!to!the!marsh!surface,!but!not!exclusively.!Currents!
also!move!sediment!along!the!edge!and!further!out!into!the!bay.!Tidal!creeks!that!
cut!through!the!marsh!further!complicate!current!patterns.!Given!dominant!flow!
!
!
48!
directions,!it!is!unlikely!that!the!tidal!creeks!provide!sediment!to!our!sites.!However,!
the!smallest!sediment!grains!with!low!settling!velocities!may!be!transported!across!
the!marsh!to!the!creek!without!depositing.!The!higher!current!velocities!moving!
towards!that!direction!would!aid!this!process.!Given!the!complex!hydrodynamics,!
models!predicting!sediment!deposition!on!marsh!islands!should!not!assume!that!the!
amount!of!sediment!deposited!on!the!marsh!is!proportional!to!the!amount!
resuspended!from!the!tidal!flat.!!
&
Wind&Waves&&
In!the!Virginia!coastal!bays,!wave!height!is!forced!by!wind!direction!and!wind!
speed.!Winds!blowing!from!the!west?northwest!(i.e.!the!direction!of!longest!fetch)!at!
speeds!greater!than!8!m!s?1!generated!the!highest!waves!at!the!study!site.!Typically,!
these!conditions!occurred!during!winter!storms.!!
As!waves!propagated!from!Hog!Island!Bay!onto!the!tidal!flat,!wave!height!
increased.!This!may!be!attributable!to!processes!such!as!wave!shoaling!or!
refraction.!For!any!given!depth,!increased!wave!height!increased!wave!shear!stress!
on!the!tidal!flat,!thus!increasing!resuspension!and!erosion!potential.!Due!to!the!tidal!
flat’s!higher!elevation!relative!to!the!lagoon,!water!depths!are!shallower.!The!
combined!influence!of!higher!waves!and!shallower!depths!increased!total!bed!shear!
stress!on!the!tidal!flat!compared!to!the!lagoon.!!
As!waves!propagated!from!the!tidal!flat!across!the!marsh!platform,!they!
quickly!dissipated!due!to!shallow!water!depths!and!the!presence!of!marsh!
vegetation!(Möller!et!al.!1999).!At!site!A,!shallower!depths!(tbl!2.4)!and!higher!
!
!
49!
biomass!density!(tbl!3.2)!resulted!in!greater!wave!dissipation!relative!to!site!B,!
despite!similar!wave!conditions!recorded!at!TAF!and!TBF.!!
!
Shear&Stress&Regimes&
When!winds!blew!from!a!W?NW!direction!at!speeds!exceeding!8!m!s?1,!
maximum!bed!shear!stresses!coincide!with!water!elevations!between!MSL!and!
MHHW,!the!range!associated!with!stable!marsh!platforms!(Fagherazzi!&!Wiberg!
2009).!Above!MHHW,!elevations!typically!associated!with!storm!surge,!bed!shear!
stress!declined!with!increasing!depth.!These!findings!agree!with!Fagherazzi!&!
Wiberg’s!(2009)!model.!However,!their!model!showed!a!decline!in!total!shear!stress!
between!MLLW!and!MSL!due!to!higher!depths!reducing!shear!stress!despite!slight!
increases!in!wave!height.!!Our!data!did!not!reveal!a!decline!in!total!shear!stress!
between!MLLW!and!MSL.!!!
A!trade!off!exists!between!elevated!SSC!on!the!tidal!flat!and!prolonged!marsh!
inundation.!At!Chimney!Pole,!the!highest!bed!shear!stress!on!the!tidal!flat!was!
produced!by!wave!events!that!occurred!during!neap!tide!when!the!marsh!barely!
flooded!(fig.!2.13,!2.14).!These!events!also!produced!the!highest!SSC,!although!very!
little!sediment!reached!the!marsh!platform!due!to!infrequent!flooding.!Similar!wind!
conditions!during!spring!tide!or!storm!surge!events!did!not!produce!as!high!bottom!
shear!stress.!!
The!highest!bed!shear!stress!on!the!tidal!flat!and!on!marsh!edge!did!not!
overlap.!Whereas!bed!shear!stress!on!the!tidal!flat!was!greatest!during!neap!tide,!
bed!shear!stress!on!the!marsh!edge!was!greatest!during!spring!tide!when!water!
!
!
50!
depths!were!sufficient!to!sustain!wave!energy!as!waves!propagated!across!the!bay?
marsh!boundary.!Therefore,!at!the!marsh!edge,!surface!erosion!and!sediment!
remobilization!are!most!likely!during!spring!tide!and/or!large!storm!surge!events.!!!
!
&
!
!
!
51!
Chapter(3:(Effects(of(Tides,(Waves(and(Currents(on(Sediment(Resuspension,(
Flux,(and(Deposition(
(
3.1(Objectives(
Wave(induced!bed!shear!stress!is!a!primary!control!of!SSC!on!tidal!flats.!One!
objective!of!this!study!is:!What!changes!in!SSC!occur!over!tidal!flats!due!to!changing!
wave!height!and!water!depth!during!a!tidal!cycle?!In!this!chapter,!we!discuss!the!
relationship!between!SSC,!tidal!elevation!and!wave!height!both!on!the!tidal!flat!and!
the!marsh!platform.!!
The!transport!of!sediment!onto!the!marsh!depends!upon!current!magnitude!
and!direction,!and!water!surface!elevation.!A!second!objective!is:!What!is!the!effect!
of!tides!and!currents!on!sediment!transport!from!a!bay!to!an!adjacent!marsh!
surface?!We!estimate!SSC!near!the!water!surface!using!a!Rouse!profile!and!then!
calculate!sediment!flux!to!determine!the!amount!of!sediment!moving!across!the!bay(
marsh!boundary.!We!also!relate!spatial!deposition!patterns!to!biomass!density,!
sediment!properties,!and!long(term!surface!elevation!table!(SET)!records.!!!
!
3.2(Methods—Data(Collection(and(Analysis(
Measured(Sediment(Deposition(
( To!measure!sediment!deposition,!9!ceramic!tiles!were!placed!flush!on!the!
marsh!surface!at!3!distances!away!(i.e.!3!replicates!per!station)!from!the!marsh!edge!
at!transect!B.!The!ceramic!tiles!remained!on!the!marsh!for!the!duration!of!the!
November!and!March!deployments.!!A!metal!straight!edge!was!used!to!scrape!off!the!
!
!
52!
sediment!that!had!deposited!on!the!tiles!and!then!the!sediment!was!dried!and!
weighed!it.!!
!
Sediment(Characteristics(
( Sediment!collected!from!sampling!stations!along!both!transects!was!analyzed!
to!determine!water!content,!organic!content,!and!grain!size!distributions.!Sediment!
was!extracted!from!the!top!2!cm!of!the!marsh!platform!and!tidal!flat!using!a!plastic!
tube!with!a!plunger!approximately!5!in.!long!with!a!1!in.!diameter.!Six!samples!were!
gathered!from!each!station!(i.e.!tidal!flat,!marsh!edge,!mid(marsh,!and!marsh!
interior)!at!both!transects!for!a!total!of!48!samples.!!
Using!3!of!the!samples!from!each!station,!water!content!was!calculated!as!the!
weight!of!the!sample!lost!when!dried!(i.e.!wet!weight(dry!weight).!Organic!content!
was!calculated!as!the!weight!of!the!sample!lost!on!ignition!(i.e.!dry!weight(ashed!
weight).!!
With!the!remaining!3!samples,!grain!size!distribution!was!determined!using!a!
laser!diffraction!particle!size!analyzer!(Beckman!Coulter!LS!I3!320).!!First,!any!large!
organic!matter!in!the!sample!was!removed!using!a!2!mm!sieve.!!Then,!the!remaining!
organic!matter!was!dissolved!using!hydrogen!peroxide.!After!the!samples!were!
prepped,!the!PSA!was!used!to!analyze!3!subsamples!of!each!sample!(i.e.!9!samples!
per!station),!and!then!the!results!were!averaged.!!
! !
(
(
!
!
53!
Biomass(Sampling(
( Aboveground!biomass!was!sampled!at!3!stations!(marsh!edge,!middle,!and!
interior)!at!sites!A!and!B!in!November!2013.!Six!replicates!were!taken!at!each!
station.!Three!samples!were!taken!to!the!left!of!each!station!at!6!m!intervals,!and!3!
samples!were!taken!to!the!right.!A!1!ft2!quadrangle!was!used!to!mark!the!sample!
area,!and!stems!inside!the!quadrangle!were!clipped!at!the!sediment!surface!and!put!
into!plastic!bags.!The!samples!were!brought!back!to!the!lab!where!they!were!dried!
and!weighed!to!determine!biomass!weight.!!
!
Sediment(Resuspension(
( Two!types!of!optical!backscatter!sensors!(OBS)!were!used!to!measure!SSC!
both!on!and!off!the!marsh!platform.!On!the!marsh,!Campbell!Scientific®!OBS(3+!
attached!to!external!dataloggers!were!deployed.!Each!datalogger!was!placed!inside!a!
dry!box,!which!was!mounted!onto!two!6(ft.!0.75(in.!diameter!steel!rods!
approximately!1.5!m!above!the!marsh!surface.!A!metal!frame!was!staked!to!the!
marsh!surface!and!the!OBS!was!attached!at!a!45°!angle!to!limit!sediment!settling!on!
the!sensor!face,!which!can!interfere!with!light!transmission.!!
On!the!tidal!flat!and!in!the!bay,!submersible!RBR!Virtuoso(dataloggers!with!
attachable!Seapoint!Sensors,!Inc.!auto(ranging!OBS!were!utilized.!To!deploy!the!
instruments,!we!attached!two!10(ft.!0.75(in.!diameter!PVC!pipes!to!each!other,!and!
then!attached!the!logger.!!The!pipes!were!pushed!approximately!3!ft.!into!the!tidal!
flat!and!bay!bottom!so!that!the!end!of!the!logger!was!flush!with!the!ground.!The!
sensor!was!approximately!0.35!m!above!the!sediment!surface.!!!!
!
!
54!
! Data!from!both!instruments!was!filtered!by!depth!to!remove!false!
measurements!recorded!above!the!water!surface!and!during!times!when!the!water!
was!so!shallow!that!the!water!surface!interfered!with!the!return!signal.!A!
comparison!between!SSC!and!total!shear!stress!allowed!for!the!determination!of!the!
threshold!shear!stress!when!SSC!exceeded!65!mg!L(1,!approximately!the!background!
concentration.!!
!
OBS(Calibration(
! The!OBS!measured!turbidity!in!nephelometric!turbidity!units!(NTUs).!!
The!instruments!must!be!independently!calibrated!with!sediment!from!the!site!to!
yield!suspended!sediment!concentration.!To!do!this,!first!sediment!was!collected!
from!the!tidal!flat!and!mixed!with!water!to!create!a!slurry.!A!tank!was!filled!with!20!
L!of!water!and!aquarium!salt!was!added!to!create!an!environment!similar!to!ocean!
salinity!(35!ppt).!Next,!the!OBS!was!attached!to!a!2(ft.!PVC!pipe!so!that!it!could!be!
maneuvered!while!in!the!tank.!Sediment!was!added!in!small!increments,!and!after!
each!addition!the!tank!was!stirred!and!a!45!mL!water!sample!was!taken.!The!
instrument!recorded!for!at!least!1!minute!after!each!sediment!addition.!For!every!
OBS!calibration!a!total!of!20!to!25!water!samples!were!collected!!
We!followed!the!filtration!method!outlined!in!Guy!(1969)!to!determine!
concentration.!First,!glass!microfiber!filters!were!dried!and!weighed!to!obtain!a!dry!
filter!weight.!Then,!using!vacuum!filtration,!the!sediment!was!transferred!from!the!
water!sample!onto!the!filter.!The!filters!were!dried!and!weighed!a!second!time,!and!
then!the!initial!filter!weight!was!subtracted!to!obtain!the!sediment!weight.!The!
!
!
55!
sediment!weight!was!divided!by!the!water!volume!filtered!(45mL)!to!yield!
concentration.!Finally,!NTUs!were!plotted!against!sediment!concentration!to!
determine!a!conversion!curve!(Fig!3.1,!Appx.!1).!!
!
!((((((((((((Figure(3.1:(Example!of!calibration!curve.!!!!!3.3(Methods—Calculations((
Settling(Velocity(
( The!relationship!between!grain!size!and!settling!velocity!was!determined!
using!Stoke’s!Law:!
!
where!ρs!is!particle!density,!ρf!is!fluid!density,!D!is!particle!size,!and!ν!is!kinematic!
viscosity!of!the!fluid.!Stokes’!law!was!chosen!because!it!is!valid!for!slowly!moving,!
very!small!grains!with!a!particle!Reynold’s!number!(RD=!uD/!ν)!less!than!0.5.!When!
y!=!2.1319x!+!23.821!
0!
200!
400!
600!
800!
1000!
1200!
1400!
0! 100! 200! 300! 400! 500! 600!
Concentration((g/m
^3)(
NTUs(
Calibration(Curve((SN:(S8671)(
(Eq.!3.1)!
!
!
56!
this!rule!was!tested!using!approximate!settling!velocity!(~3.18!x!10(4!m!s(1)!and!the!
largest!median!grain!size!(21.64!μm),!RD=0.005,!which!suggests!Stokes’!law!is!
applicable!at!our!Chimney!Pole!sites.!!
!
SSC(Profile(
! The!OBS!provide!SSC!at!0.35!m!above!the!bed!(mab).!To!estimate!SSC!
through!the!full!water!column,!the!Rouse!Equation!was!applied!(Rouse!1937)!to!3!
grain!size!fractions!i!given!by!
!
where!ri=!(wsi/(κu★c)!is!the!Rouse!parameter!for!each!grain!size!fraction,!wsi!is!the!
particle!settling!velocity,!u★c is!current!shear!velocity!(= τ!"##/ρ(),!κ!is!von!
Karman’s!constant!(0.41),!h!is!water!depth,!z!is!the!height!in!the!water!column!at!
which!Csi!is!being!estimated.!Ca!is!the!reference!concentration!at!the!reference!
height!za!=3D50,!where!D50!is!the!median!grain!size.!The!reference!concentration!(Ca)!
was!calculated!using!Smith!and!McLean’s!(1977)!equation:!
!
where!S=(τb!–!τcr)/!τcr!is!the!excess!shear!stress!determined!from!τb,!the!wave(
current!(or!total)!bed!shear!stress.!Critical!shear!stress!was!determined!to!be!τcr!
=0.07!Pa!by!examining!relationship!between!SSC!and!total!shear!stress.!This!value!
agrees!with!threshold!for!motion!curves!(Shields!1936;!Miller!et!al.!1977).!A!value!of!
γ=5e(4,!the!resuspension!coefficient,!was!chosen!by!adjusting!the!peaks!in!estimated!
(Eq.!3.2)!
(Eq.!3.3)!
!
!
57!
SSC!to!match!the!peaks!in!measured!SSC.!Field!and!laboratory!studies!have!shown!
large!variation!in!values!of!γ!,!ranging!from!10(2!to!10(5!(e.g.!Smith!and!McLean!1977;!
Wiberg!and!Smith!1983;!Sternberg!et!al.!1986;!Hill!et!al.!1988;!Drake!and!Cacchione!
1989).!A!value!of!Cbed=0.3,!the!bed!concentration!of!the!sediment,!was!used!in!Eq.!
3.3.!
SSC!profiles!calculated!with!Eq.!3.1!were!used!to!estimate!SSC!in!the!upper!
portion!of!the!water!column!when!water!depths!exceeded!the!surface!elevation!of!
the!marsh.!This!was!necessary!in!order!to!accurately!represent!the!amount!of!
sediment!advected!across!the!bay(marsh!boundary.!In!addition,!total!sediment!mass!
within!the!water!column!was!approximated!by!integrating!the!profile!obtained!
using!Eq.!3.1!for!each!time!step!(15!min,!to!conform!to!the!measurement!interval!for!
waves,!currents,!and!SSC).!Total!mass!provided!a!way!to!account!for!sediment!
retained!in!suspension!(i.e.!not!redeposited)!between!time!steps!in!addition!to!
accounting!for!sediment!resuspension.!This!is!important!because!sediment!at!our!
sites!is!very!fine!and!settles!slowly.!Using!three!size!fractions!with!varying!settling!
velocities!was!used!to!provide!a!better!estimate!of!the!amount!of!material!retained!
in!suspension!compared!to!a!single!size!fraction.!!
!
Sediment(Flux(and(Calculated(Deposition(
( Sediment!flux!was!calculated!using!the!equation:!!
(
!
(Eq.!3.4)!
!
!
58!
where!U!is!average!horizontal!sediment!velocity,!assumed!to!be!equal!to!fluid!
velocity,!Cs!is!sediment!mass!concentration,!and!h!is!water!depth.!!Measured!current!
velocity!and!modeled!SSC!near!the!surface!were!used!to!approximate!the!amount!of!
material!crossing!the!bay(marsh!boundary.!!For!flux!and!deposition,!currents!and!
SSC!were!averaged!over!the!depth!of!water!flooding!the!marsh!at!each!time!step,!
such!that!one!flux!value!was!calculated!at!each!time!step.!Flux!differences!were!used!
to!determine!sediment!deposition!between!the!marsh!edge!and!marsh!interior.!It!
was!assumed!that!all!sediment!in!suspension!was!deposited!evenly!over!the!marsh!
in!the!area!between!the!marsh!edge!and!marsh!interior,!roughly!15!m!away.!
Deposition!was!calculated!for!15!minute!intervals,!which!was!the!length!of!time!over!
which!the!flux!difference!was!calculated.!To!estimate!total!deposition!over!the!
length!of!the!4!week!deployment,!average!deposition!per!15!minutes!was!multiplied!
by!the!total!time!the!current!direction!was!approximately!perpendicular!to!the!
marsh!edge!(i.e.!orientation!of!the!sediment!plates).!
!
3.4(Results(
Measured(Sediment(Deposition((
At!our!Chimney!Pole!sites,!no!sediment!deposited!on!the!marsh!surface!near!
the!edge!(tbl!3.1).!Maximum!deposition!occurred!at!the!mid(marsh!sediment!plates!
(~8!m!from!the!edge),!and!there!was!also!some!deposition!further!into!the!marsh!
interior!(~15!m!from!the!edge).!!!
!
(
!
!
59!
( Sediment(Deposition((g(cmT2)(Location((Distance(from(edge)( NovTDec(2013( March(2014(Edge!(~2!m)! 0!±!0! 0!±!0!Middle!(~8!m)! 0.024!±!0.015! 0.036!±!0.009!Interior!(~15!m)! 0.001!±!0.001! 0.019!±!0.01!
(Table(3.1:(Average!sediment!deposited!(g!cm(2)!at!three!distances!away!from!the!bay(marsh!boundary!at!transect!B!during!the!November(December!2013!and!March!2014!deployments.!!!
Sediment(Characteristics(
Grain!size!analysis!revealed!an!overall!decrease!in!mean!particle!size!from!
the!tidal!flat!to!the!marsh!interior!at!site!A,!however!this!decrease!was!not!linear.!
We!recorded!larger!D16,!D50,!and!D84!particle!sizes!at!both!the!edge!and!mid(marsh!
relative!to!the!tidal!flat!and!interior!(tbl!3.2,!fig!3.2).!At!site!B,!grain!size!increased!
from!the!tidal!flat!to!the!marsh!interior!for!the!3!size!classes.!!
At!all!stations,!approximately!16%!of!the!bed!is!clay!(<4!μm).!At!least!84%!of!
the!bed!is!silt!!(<!63!μm)!or!smaller!at!all!stations!except!for!the!transect!B!middle!
and!interior!stations,!where!silt!accounted!for!slightly!less!of!the!bed!composition!(>!
75%).!The!remaining!sediment!was!very!fine(grained!sand.!!
! Sediment!on!the!tidal!flat!has!7(9!%!higher!water!and!is!composed!of!1(3%!
more!organic!matter!than!sediment!in!the!marsh!interior!(tbl.!3.3).!Biomass!was!
lower!on!the!marsh!edge!and!highest!in!the!marsh!interior!at!our!sites.!Low!biomass!
at!the!edge!coincided!with!low!allochthonous!sediment!deposition.!!
!
!
!
!
!
!
60!
Transect( Stations( D16( D50( ws((m(sT1)(for(D50(( D84(
A! Tidal!Flat! 2.13!±!0.26! 12.56!±2.82! 1.07!x!10(4! 36.77!±7.47!A! Marsh!Edge! 2.74!±!0.66! 18.73!±!5.66! 2.38!x!10(4! 51.08!±!12.13!A! Marsh!Middle! 3.015!±!0.54! 21.51!±!3.75! 3.14!x!10(4! 57.72!±12.13!A! Marsh!Interior! 1.68!±!0.47! 9.53!±!4.74! 6.17!x!10(5! 31.62!±!14.67!! !B! Tidal!Flat! 2.10!±!0.13! 11.42!±!1.22! 8.86!x!10(5! 33.41!±!5.95!B! Marsh!Edge! 2.19!±!0.21! 14.10!±2.23! 1.35!x!10(4! 44.01!±!6.14!B! Marsh!Middle! 2.80!±!0.57! 21.64!±!3.39! 3.18!x!10(4! 67.26!±!8.63!B! Marsh!Interior! 3.11!±!0.50! 21.64!±!3.39! 3.18!x!10(4! 67.26!±!8.63!
(Table(3.2:(Grain!size!(μm)!averaged!over!3!samples!(9!subsamples)!taken!at!each!station.!Values!given!are!for!the!16th,!50th,!and!84th!percentiles.!Settling!velocity!(ws)!was!estimated!for!D50!using!Stokes’!law!!!!
!Figure(3.2:(Percentage!of!sample!less!than!a!given!grain!size.!Samples!were!taken!from!4!stations!along!transect!A!(left)!and!transect!B!(right)!
!!Site( Station( Water((%)( Organic(Matter((%)( Biomass((g(ftT2)(A! Tidal!Flat! 51.15!±!3.58! 8.18!±!1.46! n/a!A! Edge! 48.96!±!4.48! 11.24!±!2.96! 4.87!±!1.11!A! Middle! 49.28!±!4.80! 9.63!±!1.77! 6.16!±!2.49!A! Interior! 44.04!±!1.24! 5.97!±!0.48! 7.59!±!3.83!! ! ! ! !B! Tidal!Flat! 47.66!±!3.34! 6.15!±!1.81! n/a!B! Edge! 44.39!±!3.27! 6.73!±!1.02! 4.05!±!2.49!B! Middle! 31.53!±!4.36! 3.32!±!0.96! 2.98!±!0.49!B! Interior! 38.47!±!3.21! 4.47!±!5.2! 6.37!±!2.38!
(
0 10 20 30 40 50 60 70 8010
20
30
40
50
60
70
80
90
grain size [um]
<%
Tidal FlatMarsh EdgeMarsh MiddleMarsh Interior
0 20 40 60 80 10010
20
30
40
50
60
70
80
90
grain size [um]
<%
Tidal FlatMarsh EdgeMarsh MiddleMarsh Interior
!
!
61!
Table(3.3:(Average!water!fraction!(%)!and!average!organic!matter!fraction!(%)!of!sediment!samples!taken!from!each!stations!along!transects!A!and!B.!Vegetation!was!sampled!in!November!to!yield!average!biomass!(g!ft(2).!!!!!Sediment(Resuspension(
Tidally!averaged!SSC!obtained!from!the!OBS!(0.35!mab)!was!positively!
correlated!with!tidally!averaged!significant!wave!height!when!waves!exceeded!0.1!
m!(fig!3.3).!!In!general,!the!relationship!between!SSC!and!wave!height!was!similar!at!
TAF,!TBF,!and!TBB.!!
Measured!SSC!at!all!sites!varied!overtime!in!response!to!changing!bottom!
shear!stress!(fig!3.4).!On!the!tidal!flat,!SSC!near!the!bed!(0.35!mab)!was!3!to!5!times!
higher!than!the!background!concentration!(~65!mg!L(1)!when!relatively!large!wave!
events!occurred!during!neap!tide!cycles.!Background!concentration!depicted!is!
slightly!variable!due!to!differences!in!instrumentation!and!calibration!error,!
however!background!SSC!ranged!from!50!to!80!mg!L(1.!On!the!tidal!flat!the!
correlation!between!SSC!and!wave(induced!shear!stress!was!67%,!whereas!the!
correlation!between!SSC!and!current(generated!shear!stress!was!only!2%.!Further!
away!from!the!marsh!edge!in!the!bay!(TBB),!the!correlation!between!SSC!and!wave!
shear!stress!was!51%.!There!were!no!current!measurements!taken!at!TBB.!!
Figure!3.5!shows!the!relationship!between!near(bed!SSC!and!wave(generated!
shear!stress!at!TBB!and!TBF.!There!was!a!positive!correlation!between!SSC!and!
wave(induced!shear!stress!at!TBF!and!TBB.!The!relationship!between!SSC!and!
bottom!shear!stress!is!complicated!by!the!fact!that!SSC!remains!elevated!even!after!
bed!shear!stress!declines!due!to!low!settling!velocities!and!changing!tidal!stage.!
!
!
62!
During!large!wave!events!in!November,!SSC!on!the!tidal!flat!was!16(19%!higher!at!
TBF!than!TBB.!!
!!!!!! !(
Figure(3.3:(Relationship!between!tidally!averaged!significant!wave!height!(m)!and!SSC!(mg/L)!recorded!at!TAF!(left)!and!at!TBB!and!TBF!(right)!during!November(December!2013.!!(
!
0.05 0.1 0.15 0.2 0.2560
80
100
120
140
160
180
200Transect A
Hs [m]
SSC
[mg/
L]
0.05 0.1 0.15 0.2 0.2560
80
100
120
140
160
180
200Transect B
Hs [m]
SSC
[mg/
L]
Tidal Flat A Tidal Flat B
Bay B
!
!
63!
!
Figure(3.4:(From!top!to!bottom:!depth!(m),!total!shear!stress!(Pa)!generated!by!both!currents!and!waves,!and!SSC!(mg!L(1)!recorded!at!TBF,!TBE,!TBI!during!November(December!2013.!!
!!
320 325 330 335 340 345 3500
0.5
1
1.5
2
Dep
th [m
]
Tidal Flat Edge Interior
320 325 330 335 340 3450
0.2
0.4
Tota
l She
ar S
tress
[Pa]
320 325 330 335 340 3450
100
200
300
400
500
Day of 2013
SSC
[mg/
L]
!
!
64!
!!Figure(3.5:(SSC!(mg!L(1)!as!a!function!of!wave!shear!stress!(Pa)!recorded!at!TBF!(white)!and!TBB!(blue)!during!November(December!2013.!!
!
SSC(on(the(Marsh(
The!largest!wave!events!did!not!elevate!SSC!over!the!marsh!because!the!
events!occurred!during!neap!tide!when!the!marsh!rarely!flooded.!During!periods!of!
marsh!inundation,!SSC!recorded!on!the!marsh!was!similar!to!the!background!
concentration!recorded!on!the!tidal!flat!(fig.!3.4).!SSC!at!the!marsh!edge!was!about!
45%!higher!than!SSC!in!the!interior!at!transect!B!in!November(December!2013.!
However,!interior!SSC!was!more!variable!(5(207!mg!L(1)!than!edge!SSC!(40(120!mg!
L(1).!Average!sediment!mass!(=!SSC!x!depth)!was!higher!in!the!interior!(30!g!m(2)!
than!near!the!edge!(19!g!m(2)!in!November(December!2013.!At!the!edge!and!the!
!
!
65!
interior,!the!correlation!between!current!and!wave(generated!bed!shear!stresses!
and!SSC!was!less!than!25%.!The!correlation!between!SSC!at!the!edge!and!interior!
and!current!shear!stress!on!the!tidal!flat!is!27%!and!16%,!respectively.!!The!
correlation!between!SSC!at!the!edge!and!interior!and!wave!shear!stress!on!the!tidal!
flat!is!less!than!1%!and!7%,!respectively.!!!
!
Sediment(Flux(and(Calculated(Deposition(
Sediment!transport!across!the!bay(marsh!boundary!relies!on!tidal!
inundation!and!advection!by!currents!of!SSC(bearing!water!from!the!flats!to!the!
marsh.!In!order!to!estimate!sediment!transport!to!the!marsh,!we!must!be!able!to!
adequately!estimate!SSC!in!the!water!flooding!the!marsh.!Figures!3.6!and!3.7!show!
changes!in!recorded!and!calculated!SSC!in!response!to!changing!bottom!shear!stress!
at!TBF!and!TAF.!Overall,!there!was!approximately!a!50%!correlation!between!
recorded!SSC!and!calculated!SSC!at!0.35!mab!for!both!the!1!and!3!grain!size!fractions!
(fig!3.6).!As!indicated!by!the!Rouse!equation!(Eq!3.1),!SSC!decreases!with!height!
above!the!bed!at!a!rate!dictated!by!the!ratio!of!particle!settling!velocity!to!current!
shear!velocity.!!!
During!neap!tide!the!marsh!does!not!flood!unless!there!is!a!storm!surge!
event!(fig!3.8,!3.9).!For!example!the!marsh!only!flooded!for!approximately!6%!and!
15%!of!the!May(June!2013!and!March!2014!deployments,!respectively.!For!the!
March!deployment,!of!the!30!tidal!cycles!when!the!marsh!flooded,!19!occurred!
during!spring!tide.!During!the!May(June!deployment,!the!marsh!flooded!during!9!
tidal!cycles,!all!of!which!occurred!during!spring!tide.!!!
!
!
66!
SSC!estimated!near!the!water!surface!at!TBF!during!March!2014!(3.8)!and!
TAF!during!May(June!2013!(fig!3.9)!were!similar.!Average!sediment!flux!across!the!
bay(marsh!edge!was!comparable!during!May(!June!2013!at!TAF!(2.9!g!m(2!s(1)!and!
March!2014!at!TBF!(3!g!m(2!s(1)!(fig!3.8,!3.9).!Average!sediment!deposition!was!
calculated!to!be!0.0019!±!0.003!g!cm(2!and!0.0083!±!0.005!g!cm(2!per!15!minutes!that!
the!flow!was!from!the!edge!to!the!interior!(tbl!3.4).!Total!calculated!deposition!for!
the!4!weeks!was!0.032!g!cm(2!for!May!and!0.025!g!cm(2!for!March.!!
!
!
67!
!
Figure(3.6:(From!top!to!bottom:!total!shear!stress!(Pa),!wave!shear!stress!(Pa),!current!shear!stress!(Pa),!water!depth!(m),!and!SSC(mg!L(1)!recorded!and!modeled!at!0.35!mab.!SSC!was!modeled!using!1!grain!size!and!3!grain!sizes.!For!the!3!grain!size!model,!sediment!settling!between!time!steps!was!accounted!for.!Data!were!recorded!at!TBF!during!November(December!2013.!!!
!
320 325 330 335 340 345 3500
0.2
0.4
0.6
tota
l she
ar s
tress
[Pa]
320 325 330 335 340 345 3500
0.2
0.4
0.6
wav
e sh
ear s
tress
[Pa]
320 325 330 335 340 345 3500
0.01
0.02
0.03
curr
shea
r stre
ss [P
a]
320 325 330 335 340 345 3500
1
2
3
dep
[m]
320 325 330 335 340 345 3500
100
200
300
400
SSC
[mg/
L]
Day of 2013
TBF model 1size model 3+set
!
!
68!
!!
Figure(3.7:(From!top!to!bottom:!total!shear!stress!(Pa),!wave!shear!stress!(Pa),!current!shear!stress!(Pa),!water!depth!(m),!and!modeled!SSC!(mg!L(1)!at!0.35!mab.!SSC!was!modeled!using!1!grain!size!and!3!grain!sizes.!For!the!3!grain!size!model,!sediment!settling!between!time!steps!was!accounted!for.!!Data!were!recorded!at!TAF!during!May(June!2013.!!
!
145 150 155 160 1650
0.1
0.2
0.3
0.4
tota
l she
ar s
tress
[Pa]
145 150 155 160 1650
0.1
0.2
0.3
0.4
wav
e sh
ear s
tress
[Pa]
145 150 155 160 1650
0.01
0.02
0.03
0.04
curr
shea
r stre
ss [P
a]
145 150 155 160 1650
100
200
300
400
SSC
[mg/
L]
Day of 2013
145 150 155 160 1650
0.5
1
1.5
2
dept
h [m
]
model 1size model 3+set
!
!
69!
!Figure(3.8:(From!top!to!bottom:!Depth!(m),!SSC!(mg!L(1)!estimated!at!the!top!of!the!water!column,!and!sediment!flux!(g!m(2!s(1)!above!the!marsh!platform!height!at!TBF!during!March!2014.!Flux!shown!is!total!flux!in!all!directions.!!
!!
60 65 70 75 80 85−2
−1
0
1
2
Dept
h [m
]
60 65 70 75 80 850
50
100150
200250
SSC
[mg/
L]
60 65 70 75 80 85−4
−2
0
2
4
Sed
Flux
[g/m
2 s]
Day of 2014
!
!
70!
!Figure(3.9:(From!top!to!bottom:!Depth!(m),!SSC!(mg!L(1)!estimated!at!the!top!of!the!water!column,!and!sediment!flux!(g!m(2!s(1)!above!the!marsh!platform!height!at!TAF!during!the!May(June!2013.!Flux!shown!is!total!flux!in!all!directions.!!!!!
Deployment! Flux!From:! Avg.!Sed.!Dep.!(g!cm(2)!per!15!min.!!
Avg.!Sed.!Dep.!(g!cm(2)!per!4!weeks!
May!2013! TAF! 0.0019!±!0.003! 0.025!March!2014! TBF! 0.0083!±!0.005! 0.032!!Table(3.4:(Average!sediment!deposition!calculated!from!sediment!flux!across!the!bay(marsh!boundary!at!TBF!and!TAF.!Assumes!equal!deposition!from!the!edge!to!the!interior.!!(((!
142 144 146 148 150 152 154 156 158 160 162 164−2
−1
0
1
2
Dep
th [m
]
142 144 146 148 150 152 154 156 158 160 162 1640
50
100
150
200
250
SSC
[mg/
L]
142 144 146 148 150 152 154 156 158 160 162 164−15
−10
−5
0
5
Sed
Flux
[g/m
s]
Day of 2013
!
!
71!
3.5(Discussion(
Sediment(Deposition(
In!tidal!creek!marshes,!maximum!vegetation!densities!near!the!creek!bank!
trap!sediment!and!slow!flow!velocities,!thus!promoting!sediment!deposition.!
Maximum!deposition!in!most!tidal!creek!marshes!occurs!along!the!creek(marsh!
edge!(Christiansen!1998),!whereas!maximum!deposition!at!our!site!B!occurred!
approximately!8!m!away!from!the!bay(marsh!edge,!with!additional!deposition!
further!into!the!interior!(tbl!3.5).!!Given!that!the!dominant!current!direction!on!the!
marsh!is!southeast!at!TAI,!TAE,!and!TBI,!aligning!the!sediment!plates!in!this!
direction!rather!than!perpendicular!to!the!edge!might!have!allowed!us!to!capture!
more!sediment.!
No!deposition!was!recorded!near!the!marsh!edge!during!two!separate!
deployments!at!transect!B.!Sediment!deposition!was!not!measured!at!transect!A,!
however!long(term!SET!records!at!transect!A!also!indicate!surface!erosion!along!the!
marsh!edge!near!Transect!A!(P.L.!Wiberg,!personal!communication).!Both!sparse!
vegetation!and!the!presence!of!wave!action!on!the!marsh!surface!near!the!edge!
likely!inhibit!sediment!deposition!or!permit!resuspension!of!any!sediment!that!does!
deposit.!As!a!result,!currents!carry!sediment!further!into!the!marsh!interior!until!a!
point!where!particles!are!able!to!settle!onto!the!surface.!!
As!shown!in!table!3.5,!the!amount!of!sediment!deposited!along!the!creek!
bank!in!Phillips!creek!marsh!is!similar!to!the!amount!deposited!~8!m!away!from!the!
edge!on!Chimney!Pole.!However,!the!deposition!occurred!during!two!weeks!at!
!
!
72!
Phillips!Creek!and!during!4!weeks!at!Chimney!Pole.!Therefore,!maximum!deposition!
rates!at!Phillips!Creek!appear!to!be!higher!than!at!Chimney!Pole.!!
Site:! Chimney!Pole! Phillips!Creek!(Christiansen!1998)!
Measurement!Interval! 4!weeks! 2!weeks!Timing!of!Measurement! Nov!2013! Mar!2014! Feb!1998! May(Jul!1997!Deposition!(g/cm2)!at!edge! 0! 0! 0.04! 0.004(0.024!Deposition!7(8!m!from!edge! 0.024! 0.036! 0.015! 0.002(0.009!!Table(3.5:(Comparison!of!measured!total!deposition!at!Phillips!Creek!Marsh!and!Chimney!Pole!Marsh.!!
!
Sediment(Characteristics(!Organic!matter!lowers!the!bulk!density!of!the!sediment!(Feagan!et!al.!2009),!
thereby!increasing!porosity.!At!the!tidal!flat!and!the!interior,!increased!porosity!due!
to!higher!organic!content!may!have!resulted!in!increased!water!content.!Lawson!
(2004)!and!McLoughlin!(2010)!found!a!positive!relationship!between!median!grain!
size!and!organic!content!at!Bay!and!Marsh!sites!in!Hog!Island!Bay.!However,!our!
results!do!not!confirm!this.!The!dense!upper!layer!of!root!mat!at!Chimney!Pole!
complicated!sediment!collection!at!the!edge!and!marsh!middle!stations.!!
At!transect!A,!D16,!D50,!D84!sediment!sizes!increased!from!the!marsh!edge!to!
the!middle!marsh,!then!decreased!from!the!middle!marsh!to!the!interior.!At!transect!
B,!D16,!D50,!and!D84!sediment!sizes!increased!from!the!edge!to!the!interior.!This!is!
opposite!to!the!trends!found!in!tidal!creek!marshes,!where!grain!size!decreases!with!
distance!away!from!the!creek!bank!due!to!larger!particles!settling!out!of!suspension!
first.!!
At!the!marsh!edge,!wave!shear!stress!exceeded!threshold!shear!stress!(0.07!
Pa)!3%!in!May(June!2013!(TAE),!5%!in!November(December!2013!(TBE),!and!16%!
!
!
73!
in!March!2014!(TBE).!In!the!marsh!interior,!wave!shear!stress!exceeded!threshold!
shear!stress!1%!in!May(June!2013!(TAI)!and!5%!in!November(December!2013!
(TBI).!It!is!possible!that!high!shear!stresses!near!the!edge!prevent!particles!from!
settling!out!of!suspension.!As!a!result,!grains!settle!further!into!the!marsh!interior.!!
Based!on!shear!stress!alone,!sediment!remobilization!on!the!marsh!is!
possible,!unlike!tidal!creek!marshes!where!surface!shear!stresses!are!below!the!
threshold!of!motion!(Christiansen!et!al.!2000).!However,!if!at!least!7.5%!of!the!bed!
sediment!is!clay(sized!(<!4!μm),!the!bed!typically!behaves!cohesively!(van!Ledden!et!
al.!2004),!which!can!increase!the!critical!shear!stress!(Parchure!&!Mehta!1985;!
Mitchener!&!Torfs!1996)!and!alter!size(selective!particle!entrainment!from!the!bed!
(Law!et!al.!2013).!On!Chimney!Pole,!16%!of!the!bed!was!less!than!4!μm!at!all!
sampling!locations.!Wave!action!on!the!marsh!surface!near!the!edge!may!also!
increase!bed!compaction!and!alter!sediment!strength.!In!addition,!the!marsh!surface!
has!a!dense!root!system,!which!increases!sediment!shear!strength!and!erosion!
resistance!(Pestrong!1969).!Together,!these!factors!lower!the!likelihood!of!sediment!
remobilization!on!the!marsh!surface.!!
(
Sediment(Resuspension! !(
The!amount!of!sediment!in!suspension!depends!on!total!bed!shear!stress!due!
to!waves!and!currents,!shear!velocity!in!the!water!column,!and!sediment!
characteristics!of!the!bed!(e.g.!critical!shear!stress,!porosity,!and!settling!velocity).!
On!the!tidal!flat,!SSC!and!wave(induced!shear!stress!are!well!correlated!(67%),!
whereas!SSC!is!not!correlated!with!current!shear!stress!(2%).!In!comparison!to!tidal!
!
!
74!
creek!marshes!where!tides!moving!in!and!out!of!the!creek!are!the!primary!
mechanism!of!resuspension!(Christiansen!et!al.!2000),!waves!primarily!force!
resuspension!in!open(boundary!marshes.!!
The!highest!SSC!on!the!tidal!flat!and!in!the!bay!coincided!with!relatively!large!
wave!events!generated!by!strong!winds!from!the!northwest.!Although!the!waves!
produced!SSCs!in!excess!of!300!mg!L(1,!very!little!sediment!reached!the!marsh!
platform!because!the!events!occurred!during!neap!tide!cycle!when!the!marsh!
flooded!infrequently.!As!discussed!in!chapter!1,!our!results!(in!agreement!with!
Fagherazzi!&!Wiberg!2013)!show!that!bottom!shear!stress!declines!at!elevation!
greater!than!0.6!m,!approximately!the!height!of!the!marsh.!Therefore,!sediment!
delivery!is!likely!low!during!large!wave!events!when!SSC!is!high.!This!is!important!
for!estimating!the!effect!that!such!events!have!on!marsh!sediment!accretion!and!is!
explored!further!in!Chapter!4.!!
For!wave!shear!stress!greater!than!0.1!Pa,!SSC!on!the!tidal!flat!is!higher!than!
SSC!further!out!in!the!bay.!This!suggests!that!the!critical!shear!stress!required!to!
move!the!bed!is!lower!on!the!tidal!flat!than!in!bay.!This!may!be!attributable!to!
differences!in!bed!properties,!which!were!not!measured!at!TBB.!!
!!
SSC(on(the(Marsh(
Similar!to!Chimney!Pole,!the!marsh!at!Phillips!Creek!does!not!flood!every!
tidal!cycle.!At!Phillips!Creek,!maximum!SSC!recorded!on!the!creek!bank!over!a!tidal!
cycle!was!generally!between!20(110!mg!L(1!(Christiansen!1998).!SSC!on!the!marsh!
edge!of!Chimney!Pole!falls!within!this!range,!as!it!is!similar!to!the!background!
!
!
75!
concentration!in!the!bay!(~65!mg!L(1).!At!Phillips!Creek,!variability!in!SSC!decreased!
with!distance!away!from!the!edge.!Concentrations!were!between!20(50!mg!L(1!at!7(8!
m!from!the!creek!bank.!At!Chimney!Pole,!interior!SSC!was!more!variable!(5(207!mg!
L(1)!than!SSC!at!the!edge!(40(120!mg!L(1),!which!was!typically!higher!than!interior!
SSC!when!the!marsh!was!flooded.!!Measurements!suggest!that!SSC!on!the!marsh!is!
not!well!correlated!with!wave!and!current(generated!bed!shear!stress!on!the!tidal!
flat.!!
(
Sediment(Flux(and(Calculated(Deposition!
Correlation!between!measured!and!modeled!SSC!for!November(December!
2013!(fig!3.6)!was!similar!for!both!the!1!and!3!grain!size!calculations!at!0.35!mab!
(~50%).!Therefore,!estimating!SSC!using!multiple!grain!sizes!and!accounting!for!
settling!did!not!significantly!improve!correlation!with!recorded!SSC!near!the!bed.!
However,!average!estimated!SSC!near!the!surface!is!much!lower!for!the!1!grain!size!
model!(62!mg!L(1)!than!the!3!grain!size!model!(93!mg!L(1).!!
Average!sediment!flux!across!the!boundary!was!similar!during!May!and!
March.!!Calculated!deposition!for!the!May!and!March!deployments!was!of!the!same!
order!of!magnitude!as!measured!deposition.!During!March,!the!average!sediment!
deposited!between!the!marsh!middle!and!interior!was!0.028!g!cm(2!measured!by!
sediment!plates!and!was!0.025!g!cm(2!measured!by!flux.!Deposition!measurements!
were!not!made!during!May!2013!at!transect!A.!Although!calculated!deposition!for!
May!was!similar!to!recorded!deposition!in!November!and!March,!it!may!be!over(!or!
underestimating!actual!sediment!deposition!during!May!at!site!A.!Lower!flooding!
!
!
76!
frequency!during!May!would!have!reduced!deposition!on!the!marsh,!whereas!higher!
biomass!density!during!the!summer!would!have!promoted!deposition.!Also,!the!
higher!frequency!of!on(marsh!currents!moving!sediment!across!the!marsh!edge!at!
site!A!in!May!would!have!promoted!sediment!deposition.!Overall,!if!current!
direction!and!SSC!near!the!surface!are!accounted!for,!calculating!sediment!
deposition!from!flux!seems!to!provide!a!reasonable!estimate!of!actual!deposition!on!
open(boundary!marshes.!!
!
!
77!
Chapter(4:(Estimating(Changes(in(Potential(Deposition(due(to(Sea8Level(Rise(&(
Storm(Surge(
(
4.1(Objectives(
RSLR!and!storm!surge!increase!water!depth,!thereby!allowing!larger!waves!
to!form.!An!objective!of!this!research!is:!What!impact!will!21st!century!seaClevel!rise,!
stronger!coastal!storms,!and!accompanying!changes!in!wave!conditions!have!on!
mineral!sediment!deposition!on!marsh!islands?!To!address!this!question,!we!
implemented!and!evaluated!a!model!for!windCwave!generation!in!shallow!water,!
and!the!results!were!used!to!calculate!changes!in!waveCgenerated!bottom!shear!
stress!with!changing!depth.!We!hypothesize!that!as!water!level!and!wave!height!
increase!over!the!tidal!flat,!bottom!shear!stress!also!increases!up!to!a!point!where!an!
optimum!combination!of!water!depth!and!wave!height!maximize!waveCgenerated!
bottom!shear!stress.!For!water!depths!and!wave!heights!higher!than!optimum,!we!
predict!that!bottom!shear!stress!declines.!Calculations!of!waveCgenerated!bottom!
shear!stress!were!then!combined!with!estimates!of!current!shear!velocity!based!on!
observations!to!calculate!nearCsurface!SSC!using!the!methods!outlined!in!Chapter!3.!
This!allowed!us!to!estimate!potential!deposition!on!the!marsh!under!a!range!of!wind!
and!depth!conditions.!!
!
4.2(Methods—Calculations((
Wave%Conditions%
% Data!from!meteorological!and!tidal!stations!allows!for!an!estimation!of!
!
!
78!
significant!wave!height!and!peak!period!using!the!YoungCVerhagen!(1996a,!1996b)!
parametric!model!for!finite!depth,!fetchClimited!wave!growth.!The nondimensional
wave energy ε = g2E/U4 and the nondimensional peak frequency ν= fU/g are
related to the nondimensional fetch χ= gx/U2 and the nondimensional water depth
δ= gh/U2 through the expressions:
!
where!E!is!wave!energy,!U%is!wind!speed!at!10!m!above!the!surface,%f!is!wave!
frequency,!x!is!fetch,!h%is!water!depth!along!the!fetch,!and!
!
!
!
and!
!
where!
!
!
!
From!this!significant!wave!height!Hs!and!peak!period!T%can!be!calculated:!
!
Eq.!(4.1)!
Eq.!(4.2)!
Eq.!(4.4)!
Eq.!(4.5)!
Eq.!(4.6)!
Eq.!(4.3)!
Eq.!(4.7)!
!
!
79!
(
(
The!parameters!that!must!be!specified!to!carry!out!the!wave!height!and!peak!
period!calculations!are!wind!speed,!water!depth,!and!depth!along!the!fetch.!Waves!
are!assumed!to!propagate!in!the!direction!of!the!wind.!Wind!direction!and!a!digital!
elevation!model!(DEM)!of!Hog!Island!Bay!and!its!surrounding!area!were!used!to!
calculate!fetch!and!average!depth!along!the!fetch!(Fagherazzi!&!Wiberg!2009;!
McLoughlin!et!al.!2014).!!
South!Bay!wind!data!and!Wachapreague,!VA!tide!data!were!used!to!calculate!
wave!height!and!period!during!time!periods!overlapping!with!our!observations.!
Tides!measured!at!Wachapreague!were!multiplied!by!a!previously!determined!
factor!of!1.1!to!better!represent!conditions!at!Chimney!Pole!(McLoughlin!et!al.!
2014).!Wind!data!from!South!Bay!were!used!because!the!station!captured!the!most!
likely!wind!conditions!in!Hog!Island!Bay.!!The!wind!data!were!not!multiplied!by!a!
scaling!factor!even!though!the!gauge!is!situated!at!an!elevation!less!than!10!m!(~6C7!
m).!!This!is!because!calculated!wave!heights!were!best!correlated!with!recorded!
wave!heights!when!an!adjustment!factor!was!not!used.!!
%
Bottom%Orbital%Velocity%and%Wave%Shear%Stress%
Output!from!the!YoungCVerhagen!model!was!used!to!estimate!waveCinduced!
bed!shear!stress.!First,!a!full!wave!spectrum!was!estimated!based!on!Hs,!T,!and!the!
Donelan!spectrum!(Donelan!et!al.!1985),!a!modified!form!of!the!JONSWAP!spectrum!
Eq.!(4.8)!
!
!
80!
(Wiberg!&!Sherwood!2008).!Second,!waveCgenerated!orbital!velocity!was!calculated!
for!each!frequency!band!i%of!the!surface!wave!spectrum!Sn!as!(Wiberg!&!Sherwood!
2008):!!!
!
where!
!!!!!!!!!!!!!! !
!
and! f% is! frequency! (=1/T),!h! is! depth,! and!k!is!wave!number.!WaveCgenerated!bed!
shear!stress!was!calculated!from!orbital!velocity!using!Eq.!2.5.!!!
!
Currents%
% Currents! were! estimated! at! TAF! and! TBF! using! the! relationship! between!
recorded!wind! and! currents,! and! accounting! for! the! effect! of! edge! orientation! on!
current! direction.! Time! series! of! observed! depths! and! currents!were! divided! into!
individual! tidal! cycles! and! separated! by! wind! direction,! and! then! overlaid.! This!
allowed! for! the! determination! of! variation! in! current! velocity! throughout! a! tidal!
cycle!given!either!northerly!winds!or!southerly!winds.!Current!direction!was!rotated!
by! 25°! at! TAF! and! TBF! to! account! for! the! effect! of! edge! orientation! on! current!
direction.! ! South! Bay! winds! and! Wachapreague! depth! data! were! used! in! the!
approximation.!Given! the! less!variable!nature!of! currents!at!TAF,!we!have!greater!
confidence!in!our!estimate!of!current!velocity!and!direction!at!that!site.!!
Eq.!(4.9)!
Eq.!(4.10)!
!
!
81!
SSC%%
To!evaluate!SSC!in!shallow!water,!modeled!waves!and!modeled!currents!
were!used!to!calculate!total!shear!stress!and!current!shear!velocity!(Eq.!2.1!&!2.5).!
These!calculations!were!inputted!into!the!Rouse!equation!(Eq.!3.2),!which!allows!for!
an!estimation!of!SSC!at!times!when!direct!observations!are!unavailable.!!!
To!estimate!potential!deposition!under!a!range!of!wind!and!depth!conditions,!
average!values!of!current!shear!stress!(=!9.4!x!10C4!Pa)!and!shear!velocity!(=!8.1!x!
10C4!m!sC1)!were!calculated!for!our!sites!during!the!period!of!observation.!These!
values!were!inputted!into!the!Rouse!equation,!along!with!wave!shear!stress,!in!order!
to!estimate!SSC.!Total!sediment!mass!in!the!upper!water!column!was!approximated!
by!integrating!the!Rouse!profile!at!water!elevations!above!the!marsh!height.!This!
provided!an!estimation!of!mass!available!for!potential!deposition!on!the!marsh.!!
%
4.3(Results(
Wave%Conditions%
There!is!a!77%!and!71%!correlation!between!modeled!and!recorded!wave!
heights!at!TAF!(fig.!4.1)!and!TBF!(fig.!4.2),!respectively.!For!wind!speeds!greater!
than!5!m!sC1,!at!both!sites!the!model!slightly!overestimates!waves!when!the!wind!
blows!from!the!west!and!north!(225°C360°!&!0°C45°),!and!underestimates!waves!
when!the!wind!blows!from!the!east!and!south!(90°C225°)!(fig!4.3,!4.4).!During!the!
two!large!resuspension!events!that!occurred!in!NovemberCDecember!2013,!
recorded!wave!heights!were!19%!lower!around!day!328!and!5%!higher!around!day!
332!than!estimated!wave!heights!at!TBF.!At!TAF,!recorded!wave!heights!were!16%!
!
!
82!
lower!around!day!328!and!less!than!1%!lower!around!day!332!than!estimated!wave!
heights.!!
!
Figure(4.1:(From!top!to!bottom:!wind!speed!(m!sC1)!and!wind!direction!(degrees)!recorded!in!South!Bay;!significant!wave!height!(m)!and!peak!period!(s)!recorded!at!TAF!and!predicted!using!the!YoungCVerhagen!model,!and!depth!(m)!relative!to!MSL!recorded!at!TAF!and!at!Wachapreague!(multiplied!by!a!scaling!factor!of!1.1).!!!
320 325 330 335 340 3450
10
20W
ind
Spe
ed [m
/s]
320 325 330 335 340 3450
100
200
300
Win
d D
ir [d
eg]
320 325 330 335 340 3450
0.2
0.4
0.6
Sig
Wav
e H
ght [
m]
modeled recorded TAF
320 325 330 335 340 3450
2
4
6
Pea
k W
ave
Pd
[s]
320 325 330 335 340 345
−1
0
1
Day of 2013
Dep
th [m
]
wach*1.1 recorded TAF
!
!
83!
!
Figure(4.2:(From!top!to!bottom:!wind!speed!(m!sC1)!and!wind!direction!(degrees)!recorded!in!South!Bay;!significant!wave!height!(m)!and!peak!period!(s)!recorded!at!TBF,!TBB!and!predicted!using!the!YoungCVerhagen!model,!and!depth!(m)!relative!to!MSL!recorded!at!TBF,!TBB!and!at!Wachapreague!(multiplied!by!a!scaling!factor!of!1.1).!!!!
320 325 330 335 340 3450
5
10
15
20
Win
d S
peed
[m/s
]
320 325 330 335 340 3450
100
200
300
Win
d D
ir [d
eg]
320 325 330 335 340 3450
0.2
0.4
0.6
Sig
Wav
e H
ght [
m]
modeled recorded TBF recorded TBB
320 325 330 335 340 3450
2
4
6
Pea
k W
ave
Pd
[s]
320 325 330 335 340 345
−1
0
1
Day of 2013
Dep
th [m
]
wach*1.1 recorded TBF recorded TBB
!
!
84!
!!
Figure(4.3:(Comparison!of!modeled!(blue)!and!recorded!(white)!significant!wave!height!at!TAF!for!times!when!wind!speed!exceeds!5!m!sC1!during!NovemberCDecember!2013.!!
!
!
!
85!
!Figure(4.4:(Comparison!of!modeled!(blue)!and!recorded!(white)!significant!wave!height!at!TBF!for!times!when!wind!speed!exceeds!5!m!sC1!during!NovemberCDecember!2013.!!
%
Currents%
! Fig!4.5!shows!recorded!and!modeled!currents!at!TAF!for!the!MayCJune!2013!
deployment.!There!is!a!75%!correlation!between!recorded!and!modeled!currents!
during!times!of!southerly!winds!and!the!approximately!the!same!correlation!during!
periods!of!northerly!winds.!Currents!at!the!site!follow!an!alternating!northward!
flood,!southward!ebb!pattern!in!the!presence!of!southerly!winds,!but!flow!
southward!in!the!presence!of!northerly!winds.!!!
!
!
86!
!
Figure(4.5:(From!top!to!bottom:!wind!speed!(m!sC1)!recorded!in!South!Bay!and!plotted!as!the!direction!towards!which!the!wind!is!blowing;!depth!(m)!relative!to!MSL!recorded!at!Wachapreague;!and!recorded!and!modeled!current!speed!(cm!sC1)!plotted!as!the!direction!the!water!is!flowing!towards!and!separated!by!wind!direction.!Currents!were!recorded!at!TAF!during!MayCJune!2013!and!were!modeled!for!the!same!site.!!%
%
SSC%
140 145 150 155 160 165−10
−5
0
5
10
Win
d (m
/s)
140 145 150 155 160 165−1
−0.5
00.5
11.5
Wat
erE
lev
(m)
140 145 150 155 160 165−10
−5
0
5
10
Rec
orde
d C
urre
nt (c
m/s
)
Southerly Wind Northerly Wind
140 145 150 155 160 165−10
−5
0
5
10
Mod
eled
Cur
rent
(cm
/s)
Day of 2013
!
!
87!
Using!the!Rouse!equation,!SSC!was!estimated!from!modeled!waves!and!
modeled!currents!(fig!4.6).!Overall,!there!was!a!39%!correlation!between!recorded!
SSC!at!TBF!and!modeled!SSC!for!the!3!grain!size!model!at!0.35!mab.!!
On!day!328,!waveCgenerated!shear!stress!calculated!from!recorded!waves!
was!13%!higher!than!wave!shear!stress!calculated!from!modeled!waves,!despite!
lower!recorded!wave!heights.!As!discussed!below,!this!is!likely!attributable!to!longer!
recorded!wave!period.!On!day!332,!wave!shear!stress!calculated!using!recorded!
waves!was!33%!higher!than!wave!shear!stress!calculated!for!modeled!waves.!!
Recorded!SSC!was!10C20%!higher!(at!0.35!mab)!than!estimated!SSC!during!these!
two!events!likely!due!to!higher!bed!shear!stress!(fig!4.6).!However,!mean!SSC!near!
the!surface!estimated!using!measured!waves!and!currents!was!roughly!the!same!as!
mean!SSC!estimated!using!modeled!waves!and!currents!(~93!mg!LC1),!and!the!
correlation!between!the!two!variables!was!68%.!!!
!
!
!
88!
!
Figure(4.6:(Top!panel:!Significant!wave!height!(m)!recorded!at!TBF!and!estimated!using!the!YoungCVerhagen!model.!Middle!panel:!Wave!shear!stress!(Pa)!calculated!using!recorded!waves!at!TBF!and!estimated!waves.!Bottom!panel:!SSC!at!0.35!mab!recorded!at!TBF!and!estimated!using!modeled!waves!and!modeled!currents.!SSC!was!calculated!using!either!1!or!3!grain!sizes.!For!the!3!grain!size!model,!sediment!settling!between!time!steps!was!also!accounted!for.!!!
!!Effect%of%Water%Depth%on%WaveBGenerated%Bed%Shear%Stress.%%
! Figure!4.7!shows!predicted!changes!in!wave!shear!stress!under!elevated!
depth!conditions,!which!could!be!due!to!storm!surge!or!RSLR.!Wave!shear!stress!
was!estimated!using!a!10!km!fetch!(consistent!with!the!fetch!for!winds!from!the!
west!and!northwest)!and!3!wind!speeds!(5!m!sC1,!10!m!sC1,!and!15!m!sC1).!For!a!given!
325 330 335 340 3450
0.1
0.2
0.3
0.4
0.5
Sign
ifica
nt W
ave
Hei
ght [
m]
Recorded TBF Modeled
325 330 335 340 3450
0.2
0.4
Wav
e Sh
ear S
tress
[Pa]
Recorded TBF Modeled
325 330 335 340 3450
100
200
300
SSC
[mg/
L]
Day of 2013
Recorded TBF model 1size model 3size+set
!
!
89!
depth,!wave!shear!stress!is!highest!for!the!high!wind!speed!group!and!lowest!for!the!
low!wind!speed!group.!As!wind!speed!increases,!the!depth!at!which!wave!shear!
stress!is!maximized!also!increases.!Maximum!wave!shear!stress!occurs!at!water!
depths!of!0.6!m!(τwave=0.11),!1.2m!(τwave=0.56),!and!1.6m!(τwave=1.02)!for!the!low,!
medium,!and!high!wind!speed!scenarios,!respectively.!!
!
%
Figure(4.7:(Wave!shear!stress!(Pa)!at!various!depths!(m)!calculated!using!a!full!wave!spectrum.!A!fetch!of!10km!and!3!wind!speeds!(5!m/s,!10m/s,!and!15m/s)!were!inputted!into!the!YoungCVerhagen!model!to!estimate!Hs!and!T.!!!!!!
Effect%of%Water%Depth%on%Potential%Deposition%
! Given!the!relationship!between!depth!and!wave!shear!stress!shown!in!figure!
4.7,!changes!in!SSC!(fig!4.8)!and!sediment!mass!(fig!4.9)!were!estimated!for!water!
depths!greater!than!the!marsh!height.!No!results!are!shown!for!water!depths!of!1.0!
0 0.2 0.6 1 1.4 1.8 2.2 2.6 3 00
0.2
0.4
0.6
0.8
1
1.2
1.4
Water depth [m]
Wav
e Sh
ear S
tress
[Pa]
low (5m/s)med (10m/s)high (15m/s)
!
!
90!
m!and!below!because!this!is!less!than!the!elevation!of!the!marsh!(assuming!a!mean!
water!depth!below!MSL!of!C0.5!m!and!a!marsh!elevation!above!MSL!of!0.5!m).!
Maximum!SSC!during!medium!and!high!wind!speeds!occurs!at!depths!of!1.2!and!1.8!
m,!respectively,!following!the!trends!found!in!waveCgenerated!bottom!shear!stresses!
(fig!4.8).!SSC!for!the!low!wind!speed!group!is!essentially!equal!to!the!background!
concentration!(~65!mg!LC1).!
Assuming!the!marsh!remains!at!its!current!elevation,!sediment!mass!in!the!
upper!water!column!increases!at!depths!higher!than!the!depth!associated!with!
maximum!bed!shear!stress!due!to!increased!depth!of!the!water!flooding!the!marsh,!
despite!slightly!lower!SSC!(fig!4.9).!!
!
(
Figure(4.8:(Change!in!SSC!(mg!LC1)!at!elevations!above!the!marsh!platform!height!
0 0.2 0.6 1 1.4 1.8 2.2 2.6 3 00
50
100
150
200
250
300
350
Water depth [m]
SSC
[mg/
L]
low (5m/s)med (10m/s)high (15m/s)
!
!
91!
(
Figure(4.9:(Change!in!sediment!mass!(g!mC2)!with!depth!for!water!flooding!the!marsh!platform.!Assumes!the!marsh!platform!height!remains!at!its!current!elevation!(1.0!m)!
(
4.4(Discussion!
Wave%Conditions%%
Overall,!the!YoungCVerhagen!wave!model!provides!a!good!estimate!of!
significant!wave!height!at!our!Chimney!Pole!sites.!The!correlation!is!poorer!during!
times!when!there!were!no!waves!at!the!sites!(day!336!to!339),!likely!due!to!the!
model’s!overestimation!of!peak!wave!period.!The!model!slightly!overestimates!
waves!when!the!wind!blows!from!the!west!and!north!(225°C360°!&!0°C45°)!and!
underestimates!waves!when!the!wind!blows!from!the!east!and!south!(90°C225°).!
This!could!be!attributable!to!our!calculation!of!fetch,!which!varies!with!wind!
direction.!Despite!overestimated!wave!heights!during!the!large!resuspension!event!
0 0.2 0.6 1 1.4 1.8 2.2 2.6 3 00
100
200
300
400
500
600
Water depth [m]
Sedi
men
t Mas
s [g
/m2 ]
low (5m/s)med (10m/s)high (15m/s)
!
!
92!
that!occurred!around!day!328,!measured!SSC!was!still!20%!higher!than!estimated!
SSC!due!to!higher!wave!shear!stress.!!Higher!recorded!wave!shear!stress!recorded!
on!the!tidal!flat,!despite!smaller!recorded!wave!heights,!is!likely!attributable!to!
longer!observed!wave!periods!relative!to!modeled!wave!periods.!For!NovemberC
December!2013,!average!recorded!wave!period!was!1.65!seconds!whereas!average!
modeled!wave!period!was!0.96!seconds.!!
! !!
Effect%of%Water%Depth%on%WaveBGenerated%Bed%Shear%Stress.%%
Given!a!fetch!of!10!km!and!high!wind!speed!conditions,!maximum!wave!
stress!occurs!at!a!depth!of!1.6!m.!For!comparison,!during!March!2014,!depth!at!TBF!
only!exceeded!1.4!m!for!25%!of!tidal!cycles,!which!almost!exclusively!occurred!
when!storm!surge!coincided!with!spring!tide!(see!fig!2.3).!In!the!Virginia!coastal!
bays,!high!storm!surge!is!typically!associated!with!winds!blowing!from!the!
northeast!(Fagherazzi!&!Wiberg!2009,!Mariotti!et!al.!2010).!!!
During!MayCJune!2013,!a!time!of!limited!northerly!winds!(see!fig!2.18)!and!
storm!surge,!depth!at!TBF!only!exceeded!1.4!m!for!3%!of!tidal!cycles.!A!northeast!
wind!direction!is!associated!with!low!fetch!at!our!Chimney!Pole!sites.!For!example,!
mean!fetch!calculated!for!northeast!winds!(0°C90°)!when!water!depth!exceeded!the!
marsh!elevation!was!0.29!km!for!site!A!and!0.37!km!for!site!B!in!November!2013!
(tbl!4.1).!Therefore,!maximum!wave!shear!stress!for!high!wind!speed!conditions!will!
not!likely!be!reached!via!storm!surge!because!fetch!will!be!much!less!than!10!km.!!
Moderate!increases!in!sea!level!will!force!water!levels!to!more!frequently!
exceed!1.4C1.8!m,!depths!associated!with!the!highest!wave!shear!stress.!Increased!
!
!
93!
depth!due!to!SLR!would!not!depend!on!wind!direction,!thereby!allowing!for!both!
large!fetch!and!depth!when!winds!blow!from!a!westerly!direction!(tbl!4.1).!Based!on!
the!model,!large!increases!in!RSLR!will!decrease!wave!shear!stress!for!all!wind!
speed!groups,!thereby!decreasing!SSC!on!the!tidal!flat.!!
! Although!high!wind!speed!conditions!generate!the!largest!wave!shear!stress,!
the!moderate!wind!speed!scenario!may!be!more!likely.!Wind!speeds!of!10!m!sC1!
occur!more!frequently!than!wind!speeds!of!15!m!sC1.!Observations!from!2013!
indicate!that!wind!speeds!exceeded!10!m!sC1!3.5%!of!the!year!(fig!4.10),!whereas!
wind!speeds!exceeded!15!m!sC1!less!than!1%!of!the!year.!Maximum!wave!shear!
stress!under!moderate!wind!speeds!is!much!more!likely!to!be!met!given!that!the!
maximum!occurs!at!a!depth!of!1.2!m,!and!the!current!marsh!height!is!approximately!
1!m!above!the!tidal!flat.!!
In!comparison,!for!the!high!wind!speed!scenario!maximum!wave!shear!stress!
occurs!at!a!depth!of!1.6!m.!It!is!less!likely!that!this!maximum!will!be!reached!in!the!
next!few!decades.!At!a!SLR!rate!of!4!mm!yrC1,!a!0.4!m!change!in!water!depth!would!
take!100!years!to!occur.!Over!this!time!scale,!dramatic!landscape!change!would!
likely!take!place,!especially!considering!that!some!sections!of!the!edge!are!eroding!
laterally!at!rates!greater!than!2!m!yrC1!(McLoughlin!et!al.!2014).!Even!if!wind!speeds!
increase!by!2!m!sC1!within!the!next!halfCcentury!(Young!et!al.!2011),!wind!speeds!of!
15!m!sC1!will!still!be!uncommon.!Interestingly,!91%!of!the!time!when!wind!speed!
exceeded!15!m!sC1!in!2013,!wind!direction!was!between!270C360°!(WCNW),!
indicating!that!a!long!fetch!often!accompanies!high!wind!speeds!at!the!study!site.!!
!
!
!
94!
!
Wind!direction! Mean!Fetch!(km)!at!site!A!(h>=0.65)!
Mean!Fetch!(km)!at!site!B!(h>=0.55)!
NE!(0°!C!90°)! 0.29! 0.37!SE!(90°!C!180°)! 0.19! 0.39!SW!(180°!C!270°)! 6.4! 7.9!NW!(270°!C!360°)! 5.4! 4.6!
!Table(4.1:(Mean!fetch!(km)!by!wind!direction!(degrees)!for!times!when!!!!!!!!!!water!elevation!exceeds!the!platform!height!at!sites!A!and!B!calculated!for!the!NovemberCDecember!2013!deployment.!!!!!
!
Figure(4.10:(From!left!to!right:!Cumulative!distribution!of!wind!speed!(m!sC1)!and!wind!direction!(degrees)!recorded!in!South!Bay,!and!depth!at!high!tide!(m)!relative!to!MSL!recorded!at!Wachapreague!for!the!year!of!2013.!!
!!
!!!
0 5 10 150
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Wind Spd [m/s]
Cum
ulat
ive
Dis
tribu
tion
0 100 200 3000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Wind Dir [deg]
Cum
ulat
ive
Dis
tribu
tion
−1 0 1 20
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
High Tide Dep [m]
Cum
ulat
ive
Dis
tribu
tion
!
!
95!
Effect%of%Water%Depth%on%Potential%Deposition!
! Changes!in!nearCsurface!SSC!as!water!depth!increases!roughly!parallel!
changes!in!wave!shear!stress.!Given!that!wave!shear!stress!primarily!determines!
SSC,!it!is!expected!that!maximum!SSC!will!occur!at!water!depths!corresponding!to!
maximum!bottom!shear!stress.!!
If!the!marsh!elevation!remains!constant,!increased!water!depth!on!the!marsh!
surface!increases!the!sediment!mass!in!the!water!column,!thus!increasing!potential!
deposition.!However,!this!is!highly!dependent!on!the!elevation!of!the!marsh,!which!
would!increase!if!the!marsh!keeps!pace!with!seaClevel!rise.!If!this!happens!then!the!
depth!of!the!water!flooding!the!marsh!would!remain!constant!as!total!depth!
increases!and!SSC!decreases.!This!would!result!in!decreased!sediment!mass!at!
elevations!higher!than!the!depth!associated!with!maximum!bed!shear!stress.!In!this!
case,!changes!in!sediment!mass!as!water!depth!increases!would!parallel!changes!in!
wave!shear!stress!and!SSC.!!!
! For!storm!surge!conditions,!it!is!assumed!that!the!elevation!of!the!marsh!
does!not!change!with!depth.!Therefore,!as!total!depth!increases!the!depth!of!the!
water!flooding!the!marsh!also!increases.!Based!on!our!observations,!near!surface!
SSC!during!storm!surge!likely!mirrors!the!background!concentration!due!to!little!
wave!activity,!regardless!of!total!water!depth.!Constant!SSC!and!increased!depth!of!
water!flooding!the!marsh!would!increase!sediment!mass!as!storm!surge!increases.!
While!storm!surge!could!augment!water!elevation!above!typical!spring!tide!levels!
(~0.8C1!m!above!MSL),!thereby!increasing!potential!deposition,!the!effects!of!storm!
!
!
96!
surge!versus!peak!spring!tide!on!SSC!are!uncertain!because!they!were!not!separated!
in!our!analysis!of!the!observations.!!
!
!
97!
Conclusion)
The!results!from!this!study!indicate!a!strong!correlation!between!wind!
direction!and!wave!formation,!whereby!the!largest!waves!form!when!westerly!
winds!blow!across!Hog!Island!Bay!at!relatively!high!speeds!(>!8!m!sA1).!During!this!
study,!large!waves!at!our!sites!on!Chimney!Pole!did!not!coincide!with!storm!surge!
conditions,!likely!due!to!the!fact!that!storm!surge!in!the!Virginia!coastal!bays!
generally!occurs!when!winds!blow!from!the!northeast,!a!direction!associated!with!
very!short!fetch!at!our!sites.!!
As!waves!propagated!from!Hog!Island!Bay!onto!the!tidal!flat,!wave!height!
increased.!The!combination!of!higher!waves!and!shallower!depths!increased!wave!
shear!stress!on!the!tidal!flat!relative!to!the!lagoon.!Given!strong!westerly!winds,!
maximum!bed!shear!stress!on!the!tidal!flat!occurred!at!water!elevations!between!
MSL!and!MHHW,!the!range!associated!with!stable!marsh!platforms.!Above!MHHW,!
bottom!shear!stress!declined.!The!wave!events!that!generated!the!greatest!bottom!
shear!stress!and!SSC!occurred!during!neap!tide!cycle!when!the!marsh!flooded!
infrequently.!This!is!significant!given!that!SSC!at!the!top!of!the!water!column!was!
much!higher!during!times!of!westerly!winds!exceeding!8!m!sA1!than!during!all!other!
times.!!
Like!waves,!current!patterns!on!the!tidal!flat!are!also!correlated!with!wind!
conditions.!More!typical!southerly!winds!are!associated!with!a!northward!flood,!
southward!ebb!current!pattern.!On!the!other!hand,!stronger!northerly!winds!push!
currents!southward!regardless!of!tidal!phase.!In!addition!to!winds,!the!marsh!edge!
!
!
98!
influences!current!direction!by!steering!currents!along!the!scarp!at!water!elevations!
below!the!marsh!platform!height.!!
On!the!marsh,!tidal!creeks!complicate!current!patterns.!At!3!of!the!4!marsh!
stations,!data!indicated!that!the!marsh!flooded!from!Hog!Island!Bay!and!ebbed!into!
the!tidal!creeks!backing!the!sites.!This!may!be!attributable!to!quicker!draining!of!the!
tidal!creeks!relative!to!the!bay,!as!well!as!the!steep!downward!slope!of!the!marsh!
behind!the!interior!stations.!Given!dominant!current!direction,!it!is!unlikely!that!the!
tidal!creeks!provide!sediment!to!our!sites.!For!sediment!transported!onto!the!marsh,!
high!bed!shear!stress!likely!prevented!sediment!from!depositing!near!the!marsh!
edge,!resulting!in!maximum!deposition!further!into!the!interior.!!
To!predict!future!changes!in!SSC!due!to!RSLR!and!increased!coastal!
storminess,!wave!shear!stress!was!estimated!for!various!depth!and!wind!conditions.!
For!a!fetch!of!10!km!(consistent!with!winds!from!the!west)!and!moderate!wind!
speeds!(>!10!m!sA1),!maximum!wave!shear!stress!occurs!at!a!depth!of!1.2!m.!This!
maximum!can!be!reached!under!presentAday!conditions,!but!would!occur!more!
frequently!with!moderate!SLR!and!would!be!less!sensitive!to!wind!direction.!If!the!
marsh!keeps!pace!with!SLR,!potential!deposition,!estimated!as!the!mass!of!sediment!
in!water!flooding!the!marsh,!will!also!be!maximized!at!a!depth!of!1.2!m.!However,!if!
marsh!elevation!remains!constant,!water!depths!above!1.2!m!have!the!potential!to!
increase!marsh!deposition!rates!because!while!SSC!in!the!water!flooding!the!marsh!
would!be!below!maximum!values,!the!mass!of!sediment!in!suspension!increases!
with!increasing!water!depth!above!the!marsh!platform.!!
!
!
99!
The!two!primary!factors!that!influence!sediment!deposition!on!marshes!
proximal!to!bayAmarsh!boundaries,!but!do!not!impact!tidal!creek!marshes,!are!
waves!and!current!direction.!SSC!on!the!tidal!flat!is!highly!correlated!with!wave!
shear!stress,!and!minimally!correlated!with!current!shear!stress,!the!primary!
control!of!SSC!in!tidal!creeks!(Christiansen!et!al.!2000).!However,!the!impact!of!large!
wave!events!on!sediment!deposition!at!Chimney!Pole!is!limited!by!the!fact!that!these!
events!typically!occur!when!the!marsh!is!not!flooded.!Unconstrained!flow!limits!
sediment!deposition!on!marsh!islands,!because!currents!can!carry!sediment!
towards,!but!also!away!from,!the!marsh!during!flooding!conditions.!!
Sediment!transported!onto!the!marsh!was!not!deposited!near!the!marsh!
edge.!At!our!edge!stations,!high!bed!shear!stresses!likely!prevent!sediment!from!
settling,!or!rework!it!if!it!is!temporarily!deposited.!Maximum!deposition!occurred!
further!into!the!marsh!interior.!Unlike!tidal!creek!marshes!(Christiansen!et!al.!
2000),!bed!shear!stress!may!at!times!be!high!enough!to!mobilize!sediment!on!the!
marsh!surface!at!our!sites.!Our!observations!indicate!that!deposition!occurs!during!
flooding!tides!at!rates!(0.028!(meas)!and!0.025!(calc)!g!cmA2!per!four!weeks)!that!are!
consistent!with!Christensen’s!(1998)!estimates!for!the!low!marsh!adjacent!to!
Phillips!Creek.!
!
!
!
100!
Works&Cited&&Cahoon,!D.R.!&!D.J.!Reed.!(1995).!Relationships!among!Marsh!Surface!Topography,!
Hydroperiod,!and!Soil!Accretion!in!a!Deteriorating!Louisiana!Salt!Marsh.!
Journal(of(Coastal(Research,(11(2):!357K69.!!!
Carniello,!L.,!D’Alpaos,!A.!&!A.!Defina.!(2011).!Modeling!wind!waves!and!tidal!flows!
in!shallow!microKtidal!basins.!Estuarine,(Coastal(and(Shelf(Science,(92:!263K276.!!
!
Carniello,!L.,!Defina,!A.!&!A.!D’Alpaos.!(2012).!Modeling!sandKmud!transport!induced!
by!tidal!currents!and!windKwaves!in!shallow!microtidal!basins:!Application!to!
the!Venice!Lagoon!(Italy).!Estuarine,(Coastal(&(Shelf(Science,(102K3:!105K15.!!!
Christiansen,!T.!(1998).!Sediment!Deposition!on!a!Tidal!Salt!Marsh.!(Unpublished!
PhD!Dissertation).!University!of!Virginia,!Charlottesville,!VA.!!
!
Christiansen,!T.,!Wiberg,!P.L.!&!T.G.!Mulligan.!(2000).!Flow!and!Sediment!Transport!
on!a!Tidal!Salt!Marsh!Surface.!Estuarine,(Coastal(and(Shelf(Science,(50:!315K31.!!!
D’Alpaos,!A.,!Lanzoni,!S.,!Mudd,!S.M.,!&!S.!Fagherazzi.!(2006).!Modeling!the!influence!
of!hydroperiod!and!vegetation!on!the!crossKsectional!formation!of!tidal!
channels.!Estuarine,(Coastal(and(Shelf(Science,!69!(3–4):!311–24.!!
Day!Jr.,!J.W.,!Hall,!C.S.,!Kemp,!W.M.!&!A.!YánezKArancibia.!(1989).!Estuarine(Ecology.!Hoboken:!John!Wiley!and!Sons.!
!
Day!Jr.,!J.W.,!Scarton,!F.,!Rismondo,!A.!&!D.!Are.!(1998).!Rapid!deterioration!of!a!salt!
marsh!in!Venice!Lagoon,!Italy.!Journal(of(Coastal(Research,!14:!583K90.!!
Defina,!A.,!Carniello,!L.,!Fagherazzi,!S.!&!L.!D’Alpaos.!(2007).!SelfK!organization!of!
shallow!basins!in!tidal!flats!and!salt!marshes,!Journal(of(Geophysical(Research,!112:!F03001.!
!
Donelan,!M.A.,!Hamilton,!J.,!&!W.H.!Hui.!(1985).!Directional!spectra!for!windK
generated!waves.!Philosophical(Transactions(of(the(Royal(Society(of(London,!A!315L:!509–62.!
!
Drake,!D.E.!&!D.A.!Cacchione.!(1989)!Estimates!of!the!suspended!sediment!reference!
!!!!!! concentration!(Cα)!and!resuspension!coefficient!(γ0)!from!nearKbottom!observations!on!the!California!shelf.!!Continental(Shelf(Research,!9:!51K64.!
!
Fagherazzi,!S.,!Carniello,!L.!&!A.!Defina.!(2006).!Critical!bifurcation!of!shallow!
microtidal!landforms!in!tidal!flats!and!salt!marshes,!Proceedings(of(the(National(Academy(of(Sciences(USA,!103(22):!8337–41.!
!
!
!
101!
Fagherazzi,!S.,!&!P.!L.!Wiberg.!(2009).!Importance!of!wind!conditions,!fetch,!and!
water!levels!on!waveK!generated!shear!stresses!in!shallow!intertidal!basins.!
Journal(of(Geophysical(Research,(114:!F03022.!!!
Fagherazzi,!S.,!Mariotti,!G.,!Porter,!J.H.,!McGlathery,!K.J.,!&!P.L.!Wiberg.!(2010).!Wave!
energy!asymmetry!in!shallow!bays.!Geophysical(Research(Letters,(37(24):!L24601.!
!
Fagherazzi,!S.,!Wiberg,!P.L.,!Temmerman,!S.,!Struyf,!E.,!Zhao,!Y.!&!P.A.!Raymond.!
(2013).!Fluxes!of!water,!sediment,!and!biogeochemical!compounds!in!salt!
marshes.!Ecological(Processes,(2:3.!!!!
Feagin,!R.!A.,!LozandaKBernard,!S.M.,!Ravens,!T.M.,!Möller,!I.,!Yeager,!K.M.!&!A.!H.!
Baird.!(2009).!Does!vegetation!prevent!wave!erosion!of!salt!marsh!edges?!
Proceedings(of(the(National(Academy(of(Sciences(USA,(106:!10109K13.!!
Fredsoe,!J.,!&!R.!Deigaard.!(1992).!Mechanics(of(Coastal(Sediment(Transport.!Advanced!Series!on!Ocean!Engineering!Vol.!3.!Singapore:!World!Science.!!!
!
French,!J.R.,!Spencer,!T.,!Murray,!A.L.,!&!N.S.!Arnold.!(1995).!Geostatistical!analysis!of!
sediment!deposition!in!two!small!tidal!wetlands,!Norfolk,!United!Kingdom.!
Journal(of(Coastal(Research,(11:!308–21.!!!
Friedrichs,!C.T.,!&!J.E.!Perry.!(2001).!Tidal!salt!marsh!morphodynamics,!Journal(of(Coastal(Research,!27:!6–36.!!
!
Guy,!H.P.!(1969).!Laboratory(theory(and(methods(for(sediment(analysis.!U.S.!!Geological!Survey!Techniques!of!WaterKResources!Investigations,!book!5,!
chap.!C1.!!Washington,!DC:!U.S.!Government!Printing!Office.!
!
Hill,!P.S.,!Nowell,!A.R.M.,!&!P.A.!Jumars.!(1988)!Flume!evaluation!of!the!relationship!
between!suspended!sediment!concentration!and!excess!boundary!shear!
stress.((Journal(of!Geophysical(Research,!93:!12499K510.!!
Hornberger,!G.M.,!Raffensperger,!J.P,!Wiberg,!P.L.,!&!K.N.!Eshleman.!(1998).!Elements(of(Physical(Hydrology.!Baltimore,!MD:!Johns!Hopkins!Press.!!!
!
Kirwan,!M.L.,!Guntensperger,!G.R.,!D’Alpaos,!A.,!Morris,!J.T.,!Mudd,!S.M.,!&!S.!
Temmerman.!(2010).!Limits!on!the!adaptability!of!coastal!marshes!to!rising!
sea!level.!Geophysical(Research(Letters,(37:!L23401.!!!
Kirwan,!M.L.!&!Guntenspergen,!G.R.!(2012).!Feedbacks!between!inundation,!root!
production,!and!shoot!growth!in!a!rapidly!submerging!brackish!marsh.!
Journal(of(Ecology,(100(3):!764K70.!!!
!
!
102!
Law,!B.A.,!Milligan,!T.G.,!Hill,!P.S.,!Newgard,!J.,!Wheatcroft,!R.A.,!&!P.L.!Wiberg.!
(2013).!Bed!Flocculation!on!a!muddy!intertidal!flat!in!Willapa!Bay,!
Washington,!Part!I:!A!regional!survey!of!the!grain!size!of!surficial!sediments.!
Continental(Shelf(Research,!60:!S136K44.!!!
Lawson,!S.!E.!(2004).!Sediment!Suspension!as!a!Control!on!Light!Availability!in!a!
Coastal!Lagoon.!(Unpublished!Master’s!Thesis).!University!of!Virginia,!
Charlottesville,!VA.!!
!
Lawson,!S.E.,!Wiberg,!P.L.,!McGlathery,!K.J.,!&!D.C.!Fugate.!(2007).!WindKdriven!
sediment!suspension!controls!light!availability!in!shallow!coastal!lagoon.!
Estuaries(and(Coasts,!30(1):!102K12.!!
Mariotti,!G.,!&!S.!Fagherazzi.!(2010).!A!numerical!model!for!the!coupled!longKterm!
evolution!of!salt!marshes!and!tidal!flats,!Journal(of(Geophysical(Research,(115:!F01004.!!
!
Mariotti,!G.,!Fagherazzi,!S.,!Wiberg,!P.L.,!McGlathery,!K.J.,!Carniello,!L.!&!A.!Defina.!
(2010).!Influence!of!storm!surges!and!sea!level!on!shallow!tidal!basin!erosive!
processes.!Journal(of(Geophysical(Research,(115:(C11012.!!!
Mariotti,!G.!!&!S.!Fagherazzi.!(2013).!Critical!width!of!tidal!flats!triggers!marsh!
collapse!in!the!absence!of!seaKlevel!rise.!Proceedings(of(the(National(Academy(of(Sciences(USA,!110(14):!5353–56.!!
!
Mariotti,!G.!&!J.!Carr.!(2014).!Dual!role!of!salt!marsh!retreat:!long!term!loss!and!short!
term!resilience.!Water(Resources(Research,!50(4):!2963K74.!!!
McLoughlin,!S.M.!(2010).!Erosional!Processes!along!Salt!Marsh!Edges!on!the!Eastern!
Shore!of!Virginia.!(Unpublished!Master’s!Thesis).!University!of!Virginia,!
Charlottesville,!VA.!!
!
McLoughlin,!S.M.,!Wiberg,!P.L.,!Safak,!I.,!&!K.J.!McGlathery.!(2014).!Rates!and!forcing!
of!marshKedge!erosion!in!a!shallow!coastal!bay:!Virginia.!Estuaries(and(Coasts,(DOI!10.1007/s12237K014K9841K2(
!
Mehta,!A.J.!(1988).!Laboratory!Studies!on!Cohesive!Sediment!Deposition!and!
Erosion.!Dronkers,!J.!&!van!Leussen,!W.!(Eds):!Physical(Processes(in(Estuaries!(427K45).!London:!SpringerKVerlag.!!
!
Miller,!M.C.,!McCave,!I.N.,!&!P.D.!Komar.!(1977).!Threshold!of!sediment!motion!under!
unidirectional!currents.!Sedimentology,!24:!507K27.!!!
Mitchener,!H.!and!Torfs,!H.!(1996).!Erosion!of!mud/sand!mixtures.!Journal(of(Coastal(Engineering,(29:!1K25.(
!
!
!
103!
Möller,!I.,!Spencer,!T.!&!J.!R.!French.!(1996).!Wind!wave!attenuation!over!saltmarsh!
surfaces:!Preliminary!results!from!Norfolk,!England.!Journal(of(Coastal(Research,!12(4):!1009–16.!
!
Möller,!I.,!Spencer,!T.,!French,!J.R.,!Leggett,!D.J.!&!M.!Dixon.!(1999).!Wave!
transformation!over!salt!marshes:!A!field!and!numerical!modeling!study!from!
North!Norfolk,!England.!Estuarine,(Coastal(&(Shelf(Science,!49(3):!411–26.!!!
Möller,!I.!(2006).!Quantifying!saltmarsh!vegetation!and!its!effect!on!wave!height!
dissipation:!Results!from!a!UK!East!coast!saltmarsh.!Estuarine,(Coastal(and(Shelf(Science,(69:337K51.!
!
Morris,!J.T.,!Sundareshwar,!P.V.,!Nietch,!C.T.,!Kjerfve,!B.!&!D.R.!Cahoon.!(2002).!
Responses!of!coastal!wetlands!to!rising!sea!level.!Ecology,!83:2869K77.!!
Mudd,!S.M.,!Fagherazzi,!S.,!Morris,!J.T.!&!D.J.!Furbish.!(2004).!Flow,!sedimentation,!
and!biomass!production!on!a!vegetated!salt!marsh!in!South!Carolina:!toward!
a!predictive!model!of!marsh!morphologic!and!ecologic!evolution.!In!
Fagherazzi,!S.,!Marani,!A.,!Blum,!L.K.!(Eds.),!The(Ecogeomorphology(of(Tidal(Marshes(!(pp.!165–87).!Washington,!D.C.:!American!Geophysical!Union.!!
!
Mudd,!S.M.,!Howell,!S.M.,!&!J.T.!Morris.!(2009).!Impact!of!dynamic!feedbacks!
between!sedimentation,!seaKlevel!rise,!and!biomass!production!on!nearK
surface!marsh!stratigraphy!and!carbon!accumulation.!Estuarine,(Coastal(&(Shelf(Science,(82:!377K89.!!
!
Mudd,!S.M.,!D’Alpaos,!A.!&!J.T.!Morris.!(2010).!How!does!vegetation!affect!
sedimentation!on!tidal!marshes?!Investigating!particle!capture!and!
hydrodynamic!controls!on!biologically!mediated!sedimentation.!Journal(of(Geophysical(Research,!115(F3):!F03029.!!
!
Oertel,!G.!F.!(2001).!Hypsographic,!hydroKhypsographic,!and!hydrological!analysis!of!
coastal!bay!environments,!Great!Machipongo!Bay,!Virginia.!Journal(of(Coastal(Research,(17:775K83.!
!
Parchure,!T.M.!&!A.J.!Mehta.!(1985).!Erosion!of!soft!cohesive!sediment!deposits.!
Journal(of(Hydraulic(Engineering,(111!(10):!1308K26.!!
Pestrong,!R.!(1969).!The!shear!stress!of!tidal!marsh!sediments.!Journal(of(Sedimentary(Petrology,(39:322K26.!
!
Rinaldi,!M.,!Casagli,!N.,!Dapporto,!S.!&!A.!Gargini.!(2004).!Monitoring!and!modeling!of!
pore!water!pressure!changes!and!riverbank!stability!during!flow!events.!
Earth(Surface(Processes(&(Landforms,!29:!237–54.!!!
!
!
104!
Rouse,!H.!(1937).!Modern!conceptions!of!the!mechanics!of!turbulence.!Transactions(of(the(American(Society(of(Civil(Engineers,(102:!436K505.!!
!
Rubin,!D.M.!&!!D.J.!Topping.!(2001).!Quantifying!the!relative!importance!of!flow!
regulation!and!grain!size!regulation!of!suspended!sediment!transport!α!and!
tracking!changes!in!grain!size!of!bed!sediment.!Water(Resources(Research,!37(1):!133K46.!!
!!
Shields,!A.F.(1936).!Application!of!similarity!principles!and!turbulence!research!to!
bedKload!movement,!vol!26.!Mitteilungen!der!Preussischen!Versuchsanstalt!
für!Wasserbau!und!Schiffbau,!Berlin,!Germany,!pp!5–24.!!
!
Smith,!J.!D.!&!S.R.!Mclean.!(1977).!Spatially!averaged!flow!over!a!wavy!surface.!
Journal(of(Geophysical(Research,!82:!1735–46.!!
Sternberg,!R.W.,!Cacchione,!D.A.,!Drake,!D.E.,!&!K.!Kranck.!(1986)!Suspended!
sediment!dynamics!in!an!estuarine!tidal!channel!within!San!Francisco!Bay,!
California.!Marine(Geology,(71:!237K58.!!
Stumpf,!R.P.!(1983).!The!process!of!sedimentation!on!the!surface!of!a!salt!marsh.!
Estuarine,(Coastal(and(Shelf(Science,(17(5):!495K508!!
Temmerman,!S.,!Bouma,!T.J.,!Govers,!G.,!&!D.!Lauwaet.!(2005).!Flow!paths!of!water!
and!sediment!in!a!tidal!marsh:!relations!with!marsh!developmental!stage!and!
tidal!inundation!height.!Estuaries,!28(3):!338–52.!!!
Tonelli,!M.,!Fagherazzi,!S.!&!M.!Petti.!(2010).!Modeling!wave!impact!on!salt!marsh!
boundaries.!Journal(of(Geophysical(Research,(115:!C09028.!!!
van!Ledden,!M.,!van!Kesteren,!W.G.M.,!&!J.C.!Winterwerp.!(2004).!A!Conceptual!
Framework!for!the!Erosion!Behaviour!of!sandKmud!mixtures.!Continental(Shelf(Research,(24(1):!1K11.!!
!
Wiberg,!P.L.!&!C.R.!Sherwood.!(2008).!Calculating!waveKgenerated!bottom!orbital!
velocities!from!surfaceKwave!parameters.!Computers(&(Geosciences,!34:!1243–62.!!
!
Wiberg,!P.L.!&!J.D.!Smith.!(1983)!A!comparison!of!field!data!and!theoretical!models!
for!waveKcurrent!interactions!at!the!bed!on!the!continental!shelf.((Continental(Shelf(Research,!2:!147K62.!
!
World!Health!Organization.!(2005).!Millennium(Ecosystem(Assessment:(Ecosystems(and(Human(WellIBeing—Health(Synthesis(Report.(Geneva:!WHO!Press.!!
!
!
!
105!
Young,!I.R.,!&!L.A.!Verhagen.!(1996a).!The!growth!of!fetch!limited!waves!in!water!of!
finite!depth.!1.!Total!energy!and!peak!frequency.!Coastal(Engineering,!29(1–2):!47–78.!!
!
Young,!I.R.,!&!L.A.!Verhagen.!(1996b).!The!growth!of!fetch!limited!waves!in!water!of!
finite!depth.!2.!Spectral!evolution.!Coastal(Engineering,!29(1!–!2):!79–99.!!!
Young,!I.R.,!Zieger,!S.!&!A.V.!Babanin.!(2011).!Global!Trends!in!Wind!Speed!and!Wave!
Height.!Science,!332(6028):!451K55.!!!
Zervas,!C.E.!(2001)!Sea(level(variations(of(the(United(States,(1854I1999.!(NOAA!Technical!Report!NOS!COKOPS!36).!Silver!Spring,!MD:!National!Oceanic!and!
Atmospheric!Administration.!!
!
!
!
!
! !
!
!
106!
Appendix&1&(Sensor&Serial&Number& Calibration&Curve&S8671( y=!2.1319x!+23.821!
T8397( y=2.0123x!+2.2602!
S9284( y=2.4272x!+0.7863!
54076( y=0.7786x!+81.087!
54075( y=1.024x!+48.189!
54077( y=0.8989x!+67.533!
S9346( y=1.4624x!+39.054!
!
!!
!!
y!=!2.1319x!+!23.821!
0!
200!
400!
600!
800!
1000!
1200!
1400!
0! 100! 200! 300! 400! 500! 600!
SSC&(mg/L)&
NTUs&
SN:&S8671&
y!=!2.0123x!+!2.2602!
0!
50!
100!
150!
200!
250!
300!
0! 20! 40! 60! 80! 100! 120! 140!
SSC&(mg/L)&
NTUs&
SN:&T8397&
!
!
107!
!!
!!
!
y!=!2.4272x!+!0.7863!
0!
200!
400!
600!
800!
1000!
1200!
0! 100! 200! 300! 400! 500!
SSC&&(m
g/L)&
NTUs&
SN:&S9284&
y=0.7786x!+81.087!!
0!
100!
200!
300!
400!
500!
600!
0! 100! 200! 300! 400! 500! 600! 700!
SSC&(mg/L)&
NTUs&
SN:&54076&
y!=!1.024x!+!48.189!
0!
100!
200!
300!
400!
500!
600!
700!
0! 100! 200! 300! 400! 500! 600!
SSC&(mg/L)&
NTUs&
SN:&54075&
!
!
108!
!!
!!
!
!
!
!
! !
y=0.8989x!+67.533!!
0!
100!
200!
300!
400!
500!
600!
700!
0! 100! 200! 300! 400! 500! 600!
SSC&(mg/L)&
NTUs&
SN:54077&
y!=!1.4624x!+!39.054!
0!
100!
200!
300!
400!
500!
600!
700!
0! 100! 200! 300! 400!
SSC&(mg/L)&
NTUs&
SN:&S9346&
!
!
109!
Appendix&2:&Grain&Size&Distribution&**Tables!below!show!cumulative!distribution!(%)!of!grain!size!for!each!sample!
taken!at!each!site.!Distributions!are!averages!of!the!3!subsamples!taken!for!each!
sample.!Standard!deviation!of!the!distribution!is!also!given.!!!
&&Grain&Size&(μm)&
TAE&Sample&1& TAE&Sample&2&Cum&Dist& Std&Dev& Cum&Dist& Std&Dev&
0.41! 0.34! 0.01! 0.29! 0.01!
0.45! 0.66! 0.02! 0.55! 0.01!
0.50! 1.11! 0.03! 0.94! 0.02!
0.54! 1.67! 0.05! 1.41! 0.03!
0.60! 2.33! 0.07! 1.96! 0.04!
0.66! 3.07! 0.09! 2.59! 0.05!
0.72! 3.89! 0.11! 3.27! 0.06!
0.79! 4.77! 0.14! 4.02! 0.07!
0.87! 5.70! 0.16! 4.79! 0.08!
0.95! 6.66! 0.19! 5.60! 0.09!
1.05! 7.63! 0.22! 6.41! 0.10!
1.15! 8.62! 0.26! 7.23! 0.11!
1.26! 9.61! 0.29! 8.05! 0.11!
1.38! 10.58! 0.32! 8.87! 0.12!
1.52! 11.55! 0.36! 9.67! 0.12!
1.67! 12.51! 0.39! 10.47! 0.12!
1.83! 13.47! 0.43! 11.27! 0.11!
2.01! 14.43! 0.46! 12.07! 0.11!
2.21! 15.40! 0.50! 12.88! 0.10!
2.42! 16.39! 0.54! 13.71! 0.10!
2.66! 17.42! 0.58! 14.56! 0.09!
2.92! 18.50! 0.62! 15.46! 0.08!
3.21! 19.64! 0.66! 16.41! 0.09!
3.52! 20.86! 0.71! 17.42! 0.10!
3.86! 22.16! 0.76! 18.49! 0.12!
4.24! 23.56! 0.81! 19.63! 0.15!
4.66! 25.05! 0.87! 20.85! 0.18!
5.11! 26.63! 0.93! 22.13! 0.23!
5.61! 28.31! 1.00! 23.47! 0.28!
6.16! 30.08! 1.08! 24.88! 0.33!
6.76! 31.92! 1.15! 26.33! 0.39!
7.42! 33.85! 1.24! 27.82! 0.45!
8.15! 35.84! 1.33! 29.35! 0.51!
8.94! 37.90! 1.42! 30.92! 0.58!
!
!
110!
9.82! 40.02! 1.52! 32.52! 0.65!
10.78! 42.20! 1.62! 34.16! 0.71!
11.83! 44.44! 1.73! 35.84! 0.77!
12.99! 46.74! 1.84! 37.58! 0.82!
14.26! 49.13! 1.96! 39.39! 0.85!
15.65! 51.62! 2.07! 41.29! 0.87!
17.18! 54.20! 2.19! 43.30! 0.88!
18.86! 56.89! 2.31! 45.43! 0.88!
20.71! 59.68! 2.44! 47.67! 0.88!
22.73! 62.56! 2.57! 50.05! 0.88!
24.95! 65.56! 2.71! 52.59! 0.88!
27.39! 68.66! 2.87! 55.33! 0.88!
30.07! 71.88! 3.02! 58.29! 0.88!
33.01! 75.16! 3.17! 61.48! 0.88!
36.24! 78.47! 3.29! 64.89! 0.89!
39.78! 81.70! 3.38! 68.47! 0.90!
43.67! 84.80! 3.45! 72.16! 0.92!
47.94! 87.69! 3.51! 75.86! 0.93!
52.63! 90.33! 3.56! 79.48! 0.92!
57.77! 92.64! 3.61! 82.94! 0.92!
63.42! 94.59! 3.63! 86.12! 0.93!
69.62! 96.10! 3.59! 88.94! 0.96!
76.43! 97.18! 3.45! 91.38! 1.03!
83.90! 97.87! 3.19! 93.42! 1.11!
92.10! 98.29! 2.84! 95.11! 1.19!
101.10! 98.59! 2.43! 96.51! 1.23!
110.99! 98.87! 1.96! 97.66! 1.15!
121.84! 98.73! 1.79! 98.57! 0.95!
133.75! 99.16! 1.19! 99.23! 0.65!
146.82! 99.53! 0.66! 99.66! 0.35!
161.18! 99.80! 0.29! 99.89! 0.14!
176.93! 99.94! 0.09! 99.97! 0.04!
194.23! 99.99! 0.01! 100.00! 0.01!
213.22! 100.00! 0.00! ! !
&& &
!
!
111!
Grain&Size&(μm)!
TBE&Sample&1& TBE&Sample&2& TBE&Sample&3&Cum&Dist& Std&Dev& Cum&Dist& Std&Dev& Cum&Dist& Std&Dev&
0.41! 0.36! 0.01! 0.34! 0.01! 0.38! 0.02!
0.45! 0.69! 0.02! 0.66! 0.01! 0.74! 0.03!
0.50! 1.17! 0.03! 1.11! 0.02! 1.24! 0.05!
0.54! 1.77! 0.05! 1.67! 0.03! 1.87! 0.08!
0.60! 2.46! 0.07! 2.32! 0.04! 2.61! 0.11!
0.66! 3.25! 0.10! 3.06! 0.05! 3.44! 0.14!
0.72! 4.12! 0.12! 3.88! 0.06! 4.36! 0.18!
0.79! 5.06! 0.15! 4.75! 0.08! 5.35! 0.22!
0.87! 6.05! 0.18! 5.68! 0.09! 6.39! 0.27!
0.95! 7.07! 0.21! 6.62! 0.11! 7.46! 0.32!
1.05! 8.11! 0.24! 7.59! 0.13! 8.55! 0.37!
1.15! 9.17! 0.27! 8.56! 0.15! 9.65! 0.42!
1.26! 10.22! 0.30! 9.52! 0.17! 10.75! 0.47!
1.38! 11.27! 0.32! 10.47! 0.19! 11.85! 0.53!
1.52! 12.31! 0.34! 11.41! 0.21! 12.93! 0.58!
1.67! 13.34! 0.35! 12.34! 0.24! 14.00! 0.64!
1.83! 14.37! 0.36! 13.26! 0.26! 15.07! 0.71!
2.01! 15.40! 0.36! 14.17! 0.29! 16.14! 0.77!
2.21! 16.44! 0.36! 15.10! 0.31! 17.22! 0.84!
2.42! 17.51! 0.35! 16.03! 0.34! 18.33! 0.91!
2.66! 18.61! 0.34! 17.00! 0.37! 19.48! 0.98!
2.92! 19.76! 0.33! 18.01! 0.41! 20.69! 1.06!
3.21! 20.97! 0.33! 19.08! 0.45! 21.96! 1.14!
3.52! 22.26! 0.34! 20.21! 0.49! 23.32! 1.23!
3.86! 23.64! 0.37! 21.42! 0.53! 24.76! 1.32!
4.24! 25.11! 0.41! 22.71! 0.58! 26.31! 1.40!
4.66! 26.68! 0.46! 24.09! 0.63! 27.95! 1.49!
5.11! 28.35! 0.51! 25.54! 0.68! 29.70! 1.58!
5.61! 30.11! 0.57! 27.08! 0.74! 31.54! 1.66!
6.16! 31.96! 0.62! 28.70! 0.79! 33.46! 1.74!
6.76! 33.90! 0.66! 30.38! 0.85! 35.47! 1.82!
7.42! 35.92! 0.68! 32.13! 0.91! 37.54! 1.89!
8.15! 38.02! 0.69! 33.94! 0.97! 39.67! 1.95!
8.94! 40.19! 0.68! 35.81! 1.02! 41.87! 2.01!
9.82! 42.44! 0.64! 37.73! 1.07! 44.11! 2.06!
10.78! 44.75! 0.60! 39.71! 1.12! 46.40! 2.10!
11.83! 47.15! 0.56! 41.75! 1.17! 48.73! 2.14!
12.99! 49.62! 0.55! 43.87! 1.21! 51.12! 2.18!
14.26! 52.19! 0.60! 46.07! 1.24! 53.58! 2.22!
!
!
112!
15.65! 54.87! 0.72! 48.38! 1.27! 56.12! 2.26!
17.18! 57.64! 0.88! 50.79! 1.30! 58.75! 2.31!
18.86! 60.50! 1.08! 53.32! 1.32! 61.46! 2.36!
20.71! 63.43! 1.29! 55.95! 1.33! 64.24! 2.41!
22.73! 66.39! 1.50! 58.68! 1.33! 67.07! 2.43!
24.95! 69.37! 1.69! 61.50! 1.31! 69.96! 2.43!
27.39! 72.37! 1.85! 64.43! 1.27! 72.89! 2.40!
30.07! 75.36! 1.96! 67.47! 1.22! 75.86! 2.36!
33.01! 78.31! 2.02! 70.59! 1.16! 78.83! 2.29!
36.24! 81.18! 2.03! 73.76! 1.11! 81.74! 2.23!
39.78! 83.89! 1.97! 76.92! 1.06! 84.53! 2.17!
43.67! 86.40! 1.86! 79.99! 1.01! 87.11! 2.11!
47.94! 88.66! 1.70! 82.91! 0.94! 89.45! 2.05!
52.63! 90.64! 1.52! 85.62! 0.87! 91.51! 1.98!
57.77! 92.36! 1.31! 88.08! 0.77! 93.29! 1.88!
63.42! 93.82! 1.11! 90.27! 0.66! 94.80! 1.74!
69.62! 95.06! 0.94! 92.16! 0.56! 96.05! 1.58!
76.43! 96.09! 0.81! 93.78! 0.48! 97.07! 1.41!
83.90! 96.96! 0.72! 95.16! 0.44! 97.89! 1.22!
92.10! 97.69! 0.67! 96.35! 0.44! 98.54! 1.03!
101.10! 98.33! 0.61! 97.38! 0.45! 99.04! 0.83!
110.99! 98.88! 0.52! 98.28! 0.43! 99.41! 0.61!
121.84! 99.33! 0.39! 99.00! 0.36! 99.68! 0.39!
133.75! 99.66! 0.24! 99.52! 0.25! 99.85! 0.20!
146.82! 99.87! 0.11! 99.83! 0.13! 99.95! 0.08!
161.18! 99.96! 0.03! 99.96! 0.05! 99.99! 0.02!
176.93! 99.99! 0.00! 99.99! 0.01! 100.00! 0.00!
194.23! 100.00! 0.00! 100.00! 0.00! ! !
&& &
!
!
113!
Grain&Size&(μm)&
TAI&Sample&1& TAI&Sample&2& TAI&Sample&3&Cum&Dist& Std&Dev& Cum&Dist& Std&Dev& Cum&Dist& Std&Dev&
0.41! 0.51! 0.06! 0.50! 0.03! 0.36! 0.00!
0.45! 0.98! 0.11! 0.97! 0.05! 0.69! 0.01!
0.50! 1.66! 0.19! 1.64! 0.09! 1.17! 0.02!
0.54! 2.51! 0.28! 2.46! 0.13! 1.76! 0.03!
0.60! 3.49! 0.39! 3.43! 0.18! 2.45! 0.04!
0.66! 4.61! 0.50! 4.52! 0.23! 3.23! 0.05!
0.72! 5.85! 0.62! 5.71! 0.29! 4.09! 0.07!
0.79! 7.20! 0.74! 7.00! 0.35! 5.02! 0.09!
0.87! 8.62! 0.85! 8.35! 0.41! 5.99! 0.11!
0.95! 10.10! 0.95! 9.73! 0.48! 7.00! 0.13!
1.05! 11.63! 1.03! 11.14! 0.53! 8.02! 0.15!
1.15! 13.19! 1.10! 12.55! 0.59! 9.06! 0.18!
1.26! 14.79! 1.14! 13.94! 0.64! 10.09! 0.20!
1.38! 16.41! 1.16! 15.33! 0.69! 11.12! 0.22!
1.52! 18.06! 1.15! 16.68! 0.73! 12.13! 0.24!
1.67! 19.75! 1.11! 18.02! 0.76! 13.14! 0.26!
1.83! 21.49! 1.05! 19.34! 0.79! 14.15! 0.27!
2.01! 23.29! 0.97! 20.67! 0.81! 15.16! 0.28!
2.21! 25.16! 0.87! 22.00! 0.83! 16.19! 0.28!
2.42! 27.14! 0.77! 23.37! 0.85! 17.24! 0.27!
2.66! 29.22! 0.70! 24.78! 0.86! 18.33! 0.25!
2.92! 31.43! 0.67! 26.25! 0.87! 19.48! 0.23!
3.21! 33.79! 0.70! 27.81! 0.87! 20.68! 0.20!
3.52! 36.29! 0.79! 29.48! 0.87! 21.97! 0.16!
3.86! 38.94! 0.93! 31.25! 0.87! 23.34! 0.12!
4.24! 41.72! 1.08! 33.14! 0.87! 24.79! 0.08!
4.66! 44.63! 1.24! 35.16! 0.87! 26.34! 0.06!
5.11! 47.64! 1.38! 37.29! 0.86! 27.96! 0.10!
5.61! 50.71! 1.51! 39.52! 0.86! 29.67! 0.16!
6.16! 53.81! 1.62! 41.84! 0.85! 31.44! 0.23!
6.76! 56.91! 1.70! 44.23! 0.84! 33.26! 0.31!
7.42! 59.96! 1.76! 46.69! 0.83! 35.13! 0.38!
8.15! 62.93! 1.80! 49.20! 0.82! 37.05! 0.46!
8.94! 65.80! 1.83! 51.74! 0.81! 38.99! 0.53!
9.82! 68.52! 1.84! 54.31! 0.80! 40.96! 0.60!
10.78! 71.07! 1.86! 56.90! 0.80! 42.96! 0.67!
11.83! 73.45! 1.89! 59.51! 0.81! 44.98! 0.72!
12.99! 75.67! 1.93! 62.14! 0.82! 47.05! 0.77!
14.26! 77.75! 1.98! 64.82! 0.84! 49.18! 0.81!
!
!
114!
15.65! 79.73! 2.05! 67.55! 0.86! 51.39! 0.84!
17.18! 81.62! 2.13! 70.33! 0.88! 53.69! 0.86!
18.86! 83.43! 2.22! 73.13! 0.91! 56.09! 0.87!
20.71! 85.12! 2.31! 75.92! 0.93! 58.56! 0.86!
22.73! 86.69! 2.37! 78.68! 0.96! 61.12! 0.84!
24.95! 88.14! 2.40! 81.38! 0.99! 63.77! 0.81!
27.39! 89.49! 2.39! 84.00! 1.01! 66.52! 0.78!
30.07! 90.75! 2.37! 86.54! 1.02! 69.39! 0.73!
33.01! 91.96! 2.37! 88.94! 1.02! 72.35! 0.67!
36.24! 93.11! 2.43! 91.16! 1.00! 75.35! 0.59!
39.78! 94.18! 2.53! 93.13! 0.98! 78.32! 0.49!
43.67! 95.14! 2.63! 94.80! 0.98! 81.18! 0.38!
47.94! 95.98! 2.68! 96.15! 0.99! 83.84! 0.25!
52.63! 96.70! 2.61! 97.20! 1.01! 86.26! 0.14!
57.77! 97.33! 2.43! 97.98! 1.01! 88.40! 0.04!
63.42! 97.88! 2.21! 98.57! 0.95! 90.25! 0.04!
69.62! 98.35! 2.02! 99.00! 0.83! 91.82! 0.07!
76.43! 98.72! 1.85! 99.32! 0.66! 93.12! 0.07!
83.90! 98.99! 1.65! 99.56! 0.49! 94.17! 0.05!
92.10! 99.18! 1.41! 99.74! 0.33! 95.01! 0.04!
101.10! 99.33! 1.15! 99.86! 0.20! 95.71! 0.07!
110.99! 99.49! 0.89! 99.94! 0.10! 96.36! 0.09!
121.84! 99.64! 0.62! 99.98! 0.04! 97.01! 0.09!
133.75! 99.78! 0.37! 99.99! 0.01! 97.71! 0.07!
146.82! 99.90! 0.18! 100.00! 0.00! 98.42! 0.07!
161.18! 99.97! 0.06! ! ! 99.06! 0.07!
176.93! 99.99! 0.01! ! ! 99.56! 0.07!
194.23! 100.00! 0.00! ! ! 99.85! 0.04!
213.22! ! ! ! ! 99.97! 0.02!
234.07! ! ! ! ! 100.00! 0.00!
&&& &
!
!
115!
Grain&Size&(μm)&
TBI&Sample&1& TBI&Sample&2& TBI&Sample&3&Cum&Dist& Std&Dev& Cum&Dist& Std&Dev& Cum&Dist& Std&Dev&
0.41! 0.32! 0.00! 0.24! 0.01! 0.28! 0.01!
0.45! 0.62! 0.01! 0.47! 0.03! 0.55! 0.02!
0.50! 1.05! 0.01! 0.80! 0.04! 0.94! 0.03!
0.54! 1.58! 0.02! 1.21! 0.06! 1.41! 0.05!
0.60! 2.20! 0.02! 1.69! 0.09! 1.97! 0.07!
0.66! 2.89! 0.03! 2.23! 0.11! 2.59! 0.10!
0.72! 3.66! 0.03! 2.83! 0.14! 3.29! 0.12!
0.79! 4.48! 0.03! 3.48! 0.17! 4.04! 0.15!
0.87! 5.33! 0.03! 4.16! 0.20! 4.83! 0.19!
0.95! 6.21! 0.03! 4.87! 0.22! 5.64! 0.22!
1.05! 7.10! 0.03! 5.60! 0.25! 6.48! 0.26!
1.15! 7.99! 0.03! 6.34! 0.27! 7.32! 0.29!
1.26! 8.87! 0.04! 7.08! 0.30! 8.17! 0.33!
1.38! 9.74! 0.05! 7.82! 0.32! 9.01! 0.38!
1.52! 10.60! 0.06! 8.55! 0.34! 9.85! 0.42!
1.67! 11.44! 0.07! 9.28! 0.37! 10.68! 0.46!
1.83! 12.28! 0.08! 10.00! 0.39! 11.51! 0.51!
2.01! 13.13! 0.09! 10.73! 0.42! 12.34! 0.56!
2.21! 13.98! 0.10! 11.46! 0.45! 13.18! 0.61!
2.42! 14.85! 0.11! 12.20! 0.48! 14.04! 0.66!
2.66! 15.75! 0.11! 12.96! 0.52! 14.93! 0.72!
2.92! 16.70! 0.12! 13.74! 0.57! 15.85! 0.79!
3.21! 17.70! 0.13! 14.56! 0.62! 16.81! 0.86!
3.52! 18.76! 0.14! 15.41! 0.68! 17.82! 0.93!
3.86! 19.89! 0.14! 16.32! 0.75! 18.89! 1.01!
4.24! 21.10! 0.15! 17.27! 0.82! 20.01! 1.10!
4.66! 22.38! 0.17! 18.28! 0.91! 21.20! 1.19!
5.11! 23.73! 0.18! 19.34! 1.01! 22.45! 1.29!
5.61! 25.14! 0.20! 20.46! 1.12! 23.75! 1.39!
6.16! 26.60! 0.21! 21.63! 1.24! 25.11! 1.49!
6.76! 28.11! 0.23! 22.85! 1.38! 26.51! 1.60!
7.42! 29.65! 0.25! 24.13! 1.52! 27.96! 1.70!
8.15! 31.22! 0.27! 25.45! 1.68! 29.45! 1.80!
8.94! 32.82! 0.28! 26.83! 1.85! 30.98! 1.90!
9.82! 34.45! 0.30! 28.27! 2.03! 32.56! 1.99!
10.78! 36.10! 0.30! 29.77! 2.22! 34.19! 2.07!
11.83! 37.79! 0.30! 31.34! 2.41! 35.88! 2.14!
12.99! 39.53! 0.29! 33.00! 2.59! 37.64! 2.20!
14.26! 41.35! 0.28! 34.76! 2.78! 39.50! 2.25!
!
!
116!
15.65! 43.26! 0.25! 36.65! 2.95! 41.49! 2.29!
17.18! 45.29! 0.23! 38.68! 3.11! 43.62! 2.31!
18.86! 47.42! 0.22! 40.89! 3.27! 45.91! 2.33!
20.71! 49.68! 0.21! 43.26! 3.41! 48.35! 2.34!
22.73! 52.08! 0.20! 45.83! 3.54! 50.97! 2.34!
24.95! 54.66! 0.18! 48.61! 3.65! 53.78! 2.34!
27.39! 57.46! 0.16! 51.62! 3.73! 56.80! 2.32!
30.07! 60.50! 0.17! 54.86! 3.76! 60.03! 2.29!
33.01! 63.77! 0.20! 58.33! 3.75! 63.45! 2.24!
36.24! 67.21! 0.26! 62.02! 3.67! 67.00! 2.17!
39.78! 70.74! 0.32! 65.85! 3.54! 70.61! 2.06!
43.67! 74.27! 0.37! 69.78! 3.34! 74.19! 1.93!
47.94! 77.71! 0.40! 73.72! 3.10! 77.66! 1.78!
52.63! 81.01! 0.42! 77.57! 2.79! 80.95! 1.59!
57.77! 84.10! 0.44! 81.25! 2.45! 83.99! 1.39!
63.42! 86.96! 0.46! 84.66! 2.07! 86.74! 1.19!
69.62! 89.52! 0.48! 87.71! 1.70! 89.15! 0.99!
76.43! 91.73! 0.50! 90.33! 1.36! 91.19! 0.80!
83.90! 93.55! 0.48! 92.53! 1.07! 92.87! 0.64!
92.10! 94.97! 0.43! 94.34! 0.85! 94.25! 0.50!
101.10! 96.08! 0.36! 95.86! 0.68! 95.41! 0.39!
110.99! 96.98! 0.30! 97.14! 0.55! 96.45! 0.30!
121.84! 97.77! 0.23! 98.20! 0.42! 97.41! 0.23!
133.75! 98.48! 0.17! 99.03! 0.29! 98.30! 0.17!
146.82! 99.11! 0.12! 99.59! 0.16! 99.05! 0.11!
161.18! 99.59! 0.07! 99.88! 0.06! 99.59! 0.06!
176.93! 99.87! 0.03! 99.98! 0.01! 99.88! 0.02!
194.23! 99.98! 0.01! 100.00! 0.00! 99.98! 0.00!
213.22! 100.00! 0.00! ! ! 100.00! 0.00!
&& &
!
!
117!
Grain&Size&(μm)&
TAQmiddle&Sample&1& TAQmiddle&Sample&2& TAQmiddle&Sample&3&Cum&Dist& Std&Dev& Cum&Dist& Std&Dev& Cum&Dist& Std&Dev&
0.41! 0.25! 0.02! 0.29! 0.08! 0.32! 0.00!
0.45! 0.49! 0.03! 0.56! 0.15! 0.62! 0.01!
0.50! 0.83! 0.06! 0.94! 0.24! 1.06! 0.02!
0.54! 1.25! 0.09! 1.40! 0.33! 1.59! 0.03!
0.60! 1.75! 0.13! 1.92! 0.41! 2.22! 0.04!
0.66! 2.31! 0.17! 2.48! 0.47! 2.92! 0.05!
0.72! 2.94! 0.22! 3.09! 0.51! 3.71! 0.06!
0.79! 3.63! 0.28! 3.71! 0.51! 4.55! 0.08!
0.87! 4.35! 0.34! 4.35! 0.48! 5.44! 0.09!
0.95! 5.12! 0.42! 4.99! 0.44! 6.35! 0.11!
1.05! 5.90! 0.49! 5.63! 0.39! 7.29! 0.12!
1.15! 6.71! 0.58! 6.28! 0.37! 8.24! 0.14!
1.26! 7.53! 0.67! 6.94! 0.38! 9.19! 0.16!
1.38! 8.35! 0.77! 7.62! 0.40! 10.13! 0.17!
1.52! 9.17! 0.87! 8.34! 0.44! 11.07! 0.18!
1.67! 10.00! 0.98! 9.11! 0.51! 12.01! 0.19!
1.83! 10.84! 1.10! 9.93! 0.65! 12.95! 0.20!
2.01! 11.68! 1.22! 10.81! 0.89! 13.89! 0.21!
2.21! 12.54! 1.34! 11.75! 1.23! 14.85! 0.21!
2.42! 13.41! 1.47! 12.74! 1.64! 15.83! 0.22!
2.66! 14.30! 1.60! 13.77! 2.07! 16.85! 0.22!
2.92! 15.23! 1.73! 14.83! 2.49! 17.92! 0.22!
3.21! 16.21! 1.87! 15.92! 2.88! 19.05! 0.22!
3.52! 17.23! 2.00! 17.03! 3.20! 20.26! 0.23!
3.86! 18.30! 2.13! 18.17! 3.48! 21.54! 0.23!
4.24! 19.43! 2.27! 19.35! 3.70! 22.90! 0.24!
4.66! 20.62! 2.40! 20.58! 3.90! 24.35! 0.25!
5.11! 21.87! 2.53! 21.87! 4.10! 25.89! 0.27!
5.61! 23.18! 2.66! 23.23! 4.29! 27.50! 0.29!
6.16! 24.54! 2.79! 24.64! 4.49! 29.17! 0.32!
6.76! 25.95! 2.92! 26.09! 4.68! 30.91! 0.35!
7.42! 27.41! 3.04! 27.57! 4.82! 32.70! 0.38!
8.15! 28.91! 3.17! 29.06! 4.90! 34.53! 0.41!
8.94! 30.46! 3.29! 30.54! 4.91! 36.40! 0.44!
9.82! 32.05! 3.41! 32.04! 4.86! 38.31! 0.47!
10.78! 33.69! 3.53! 33.57! 4.80! 40.24! 0.50!
11.83! 35.38! 3.64! 35.18! 4.76! 42.22! 0.52!
12.99! 37.13! 3.75! 36.88! 4.77! 44.24! 0.55!
14.26! 38.97! 3.86! 38.72! 4.86! 46.32! 0.57!
!
!
118!
15.65! 40.91! 3.97! 40.69! 4.99! 48.49! 0.59!
17.18! 42.98! 4.07! 42.76! 5.11! 50.75! 0.62!
18.86! 45.18! 4.18! 44.90! 5.15! 53.11! 0.67!
20.71! 47.51! 4.30! 47.09! 5.07! 55.56! 0.73!
22.73! 49.99! 4.42! 49.34! 4.90! 58.11! 0.79!
24.95! 52.62! 4.55! 51.72! 4.68! 60.78! 0.85!
27.39! 55.43! 4.71! 54.32! 4.49! 63.57! 0.89!
30.07! 58.43! 4.88! 57.22! 4.40! 66.52! 0.92!
33.01! 61.61! 5.09! 60.45! 4.44! 69.60! 0.95!
36.24! 64.95! 5.32! 64.00! 4.60! 72.79! 0.99!
39.78! 68.38! 5.56! 67.77! 4.79! 76.03! 1.06!
43.67! 71.86! 5.77! 71.63! 4.93! 79.25! 1.14!
47.94! 75.32! 5.92! 75.47! 4.95! 82.36! 1.23!
52.63! 78.69! 5.98! 79.16! 4.82! 85.27! 1.30!
57.77! 81.90! 5.95! 82.65! 4.56! 87.92! 1.33!
63.42! 84.87! 5.86! 85.87! 4.25! 90.26! 1.31!
69.62! 87.54! 5.74! 88.81! 3.94! 92.27! 1.26!
76.43! 89.86! 5.61! 91.44! 3.64! 93.97! 1.19!
83.90! 91.83! 5.46! 93.72! 3.32! 95.41! 1.13!
92.10! 93.48! 5.25! 95.62! 2.90! 96.63! 1.06!
101.10! 94.89! 4.91! 97.13! 2.33! 97.67! 0.97!
110.99! 96.12! 4.36! 98.24! 1.62! 98.53! 0.85!
121.84! 97.20! 3.60! 99.04! 0.97! 99.17! 0.66!
133.75! 98.12! 2.69! 99.56! 0.51! 99.60! 0.43!
146.82! 98.87! 1.78! 99.85! 0.22! 99.84! 0.22!
161.18! 99.42! 0.98! 99.96! 0.06! 99.95! 0.07!
176.93! 99.76! 0.42! 99.99! 0.01! 99.99! 0.01!
194.23! 99.93! 0.12! 100.00! 0.00! 100.00! 0.00!
213.22! 99.99! 0.02! ! ! ! !
234.07! 100.00! 0.00! ! ! ! !
&& &
!
!
119!
Grain&Size&(μm)&
TBQmiddle&Sample&1& TBQmiddle&Sample&2& TBQmiddle&Sample&3&Cum&Dist& Std&Dev& Cum&Dist& Std&Dev& Cum&Dist& Std&Dev&
0.41! 0.28! 0.01! 0.38! 0.03! 0.25! 0.02!
0.45! 0.55! 0.02! 0.74! 0.05! 0.48! 0.03!
0.50! 0.93! 0.03! 1.25! 0.09! 0.82! 0.05!
0.54! 1.40! 0.05! 1.88! 0.14! 1.24! 0.08!
0.60! 1.95! 0.07! 2.62! 0.19! 1.74! 0.11!
0.66! 2.57! 0.09! 3.44! 0.25! 2.30! 0.14!
0.72! 3.25! 0.11! 4.35! 0.31! 2.93! 0.18!
0.79! 3.99! 0.13! 5.33! 0.38! 3.61! 0.23!
0.87! 4.77! 0.16! 6.35! 0.45! 4.34! 0.28!
0.95! 5.57! 0.19! 7.39! 0.52! 5.10! 0.33!
1.05! 6.39! 0.21! 8.45! 0.59! 5.88! 0.38!
1.15! 7.22! 0.24! 9.51! 0.66! 6.69! 0.44!
1.26! 8.04! 0.27! 10.56! 0.73! 7.51! 0.50!
1.38! 8.86! 0.29! 11.59! 0.79! 8.33! 0.57!
1.52! 9.67! 0.32! 12.60! 0.86! 9.16! 0.65!
1.67! 10.47! 0.34! 13.60! 0.93! 9.99! 0.73!
1.83! 11.27! 0.37! 14.59! 1.00! 10.83! 0.82!
2.01! 12.07! 0.39! 15.57! 1.08! 11.66! 0.91!
2.21! 12.88! 0.41! 16.56! 1.15! 12.51! 1.02!
2.42! 13.70! 0.43! 17.57! 1.23! 13.37! 1.13!
2.66! 14.56! 0.46! 18.61! 1.32! 14.25! 1.25!
2.92! 15.45! 0.48! 19.69! 1.41! 15.16! 1.38!
3.21! 16.39! 0.50! 20.84! 1.50! 16.10! 1.51!
3.52! 17.38! 0.52! 22.05! 1.61! 17.08! 1.65!
3.86! 18.43! 0.55! 23.34! 1.71! 18.10! 1.80!
4.24! 19.55! 0.57! 24.71! 1.82! 19.18! 1.96!
4.66! 20.74! 0.59! 26.15! 1.94! 20.30! 2.12!
5.11! 21.99! 0.62! 27.66! 2.05! 21.48! 2.28!
5.61! 23.31! 0.64! 29.24! 2.16! 22.72! 2.44!
6.16! 24.68! 0.67! 30.85! 2.27! 24.01! 2.60!
6.76! 26.10! 0.69! 32.50! 2.37! 25.35! 2.75!
7.42! 27.57! 0.72! 34.18! 2.46! 26.74! 2.90!
8.15! 29.09! 0.74! 35.87! 2.54! 28.18! 3.04!
8.94! 30.64! 0.76! 37.57! 2.61! 29.67! 3.16!
9.82! 32.24! 0.78! 39.27! 2.67! 31.21! 3.27!
10.78! 33.88! 0.80! 40.97! 2.72! 32.80! 3.36!
11.83! 35.57! 0.82! 42.66! 2.76! 34.44! 3.43!
12.99! 37.32! 0.84! 44.35! 2.80! 36.14! 3.48!
14.26! 39.16! 0.86! 46.06! 2.84! 37.91! 3.49!
!
!
120!
15.65! 41.11! 0.88! 47.81! 2.88! 39.76! 3.48!
17.18! 43.19! 0.91! 49.59! 2.91! 41.71! 3.44!
18.86! 45.39! 0.94! 51.40! 2.93! 43.79! 3.38!
20.71! 47.74! 0.98! 53.23! 2.94! 46.00! 3.30!
22.73! 50.24! 1.03! 55.08! 2.94! 48.35! 3.20!
24.95! 52.90! 1.08! 56.94! 2.93! 50.87! 3.08!
27.39! 55.75! 1.14! 58.83! 2.92! 53.56! 2.95!
30.07! 58.80! 1.21! 60.76! 2.92! 56.42! 2.81!
33.01! 62.06! 1.30! 62.73! 2.92! 59.45! 2.66!
36.24! 65.48! 1.39! 64.77! 2.92! 62.61! 2.50!
39.78! 69.02! 1.48! 66.89! 2.90! 65.87! 2.33!
43.67! 72.61! 1.56! 69.09! 2.86! 69.19! 2.15!
47.94! 76.18! 1.61! 71.37! 2.76! 72.51! 1.98!
52.63! 79.65! 1.61! 73.73! 2.62! 75.80! 1.80!
57.77! 82.95! 1.58! 76.15! 2.44! 78.99! 1.61!
63.42! 86.02! 1.51! 78.62! 2.25! 82.05! 1.42!
69.62! 88.80! 1.44! 81.11! 2.06! 84.91! 1.22!
76.43! 91.25! 1.39! 83.61! 1.91! 87.56! 1.02!
83.90! 93.34! 1.38! 86.14! 1.79! 89.96! 0.84!
92.10! 95.10! 1.37! 88.71! 1.67! 92.13! 0.70!
101.10! 96.55! 1.32! 91.28! 1.52! 94.10! 0.62!
110.99! 97.73! 1.17! 93.76! 1.30! 95.86! 0.58!
121.84! 98.64! 0.91! 96.00! 1.00! 97.37! 0.52!
133.75! 99.29! 0.58! 97.80! 0.66! 98.57! 0.41!
146.82! 99.71! 0.28! 99.04! 0.34! 99.38! 0.25!
161.18! 99.91! 0.09! 99.70! 0.13! 99.81! 0.11!
176.93! 99.99! 0.02! 99.95! 0.03! 99.97! 0.03!
194.23! 100.00! 0.00! 100.00! 0.00! 100.00! 0.00!
&& &
!
!
121!
Grain&Size&(μm)&
TAF&Sample&1& TAF&Sample&2& TAF&Sample&3&Cum&Dist& Std&Dev& Cum&Dist& Std&Dev& Cum&Dist& Std&Dev&
0.41! 0.33! 0.01! 0.37! 0.02! 0.38! 0.03!
0.45! 0.64! 0.02! 0.73! 0.03! 0.74! 0.06!
0.50! 1.08! 0.03! 1.23! 0.05! 1.26! 0.09!
0.54! 1.63! 0.04! 1.85! 0.08! 1.89! 0.14!
0.60! 2.26! 0.06! 2.58! 0.11! 2.63! 0.20!
0.66! 2.98! 0.07! 3.41! 0.14! 3.47! 0.26!
0.72! 3.78! 0.09! 4.32! 0.18! 4.39! 0.33!
0.79! 4.64! 0.10! 5.30! 0.22! 5.38! 0.40!
0.87! 5.53! 0.12! 6.34! 0.26! 6.42! 0.47!
0.95! 6.46! 0.13! 7.41! 0.31! 7.49! 0.55!
1.05! 7.40! 0.14! 8.51! 0.35! 8.58! 0.62!
1.15! 8.35! 0.15! 9.62! 0.40! 9.68! 0.70!
1.26! 9.30! 0.15! 10.73! 0.45! 10.78! 0.77!
1.38! 10.24! 0.16! 11.84! 0.50! 11.87! 0.83!
1.52! 11.18! 0.17! 12.95! 0.55! 12.95! 0.90!
1.67! 12.10! 0.18! 14.05! 0.61! 14.04! 0.96!
1.83! 13.03! 0.20! 15.16! 0.67! 15.13! 1.03!
2.01! 13.96! 0.23! 16.28! 0.73! 16.24! 1.11!
2.21! 14.90! 0.26! 17.42! 0.80! 17.38! 1.20!
2.42! 15.87! 0.30! 18.61! 0.87! 18.57! 1.32!
2.66! 16.89! 0.35! 19.84! 0.95! 19.82! 1.47!
2.92! 17.95! 0.40! 21.15! 1.04! 21.15! 1.66!
3.21! 19.08! 0.45! 22.54! 1.12! 22.58! 1.90!
3.52! 20.29! 0.51! 24.04! 1.21! 24.12! 2.19!
3.86! 21.58! 0.56! 25.65! 1.30! 25.78! 2.54!
4.24! 22.96! 0.62! 27.38! 1.39! 27.56! 2.94!
4.66! 24.44! 0.67! 29.25! 1.48! 29.47! 3.38!
5.11! 26.01! 0.72! 31.25! 1.56! 31.49! 3.88!
5.61! 27.67! 0.77! 33.37! 1.64! 33.62! 4.42!
6.16! 29.42! 0.81! 35.62! 1.70! 35.84! 4.99!
6.76! 31.24! 0.84! 37.98! 1.76! 38.14! 5.60!
7.42! 33.13! 0.87! 40.46! 1.80! 40.50! 6.22!
8.15! 35.09! 0.90! 43.04! 1.82! 42.91! 6.86!
8.94! 37.11! 0.91! 45.71! 1.84! 45.34! 7.50!
9.82! 39.19! 0.92! 48.47! 1.83! 47.79! 8.12!
10.78! 41.34! 0.92! 51.30! 1.81! 50.23! 8.73!
11.83! 43.54! 0.90! 54.20! 1.77! 52.66! 9.29!
12.99! 45.82! 0.88! 57.16! 1.72! 55.08! 9.80!
14.26! 48.20! 0.85! 60.19! 1.67! 57.51! 10.27!
!
!
122!
15.65! 50.69! 0.81! 63.29! 1.61! 59.96! 10.69!
17.18! 53.30! 0.76! 66.45! 1.54! 62.45! 11.05!
18.86! 56.04! 0.71! 69.65! 1.48! 64.95! 11.32!
20.71! 58.90! 0.67! 72.88! 1.43! 67.44! 11.48!
22.73! 61.88! 0.65! 76.09! 1.38! 69.90! 11.52!
24.95! 64.98! 0.66! 79.25! 1.33! 72.37! 11.48!
27.39! 68.23! 0.69! 82.33! 1.28! 74.88! 11.42!
30.07! 71.61! 0.73! 85.30! 1.23! 77.49! 11.39!
33.01! 75.08! 0.75! 88.09! 1.19! 80.23! 11.41!
36.24! 78.58! 0.75! 90.66! 1.15! 83.05! 11.40!
39.78! 82.02! 0.72! 92.94! 1.14! 85.85! 11.26!
43.67! 85.28! 0.65! 94.89! 1.15! 88.47! 10.91!
47.94! 88.26! 0.57! 96.47! 1.18! 90.74! 10.33!
52.63! 90.88! 0.47! 97.68! 1.19! 92.59! 9.62!
57.77! 93.10! 0.37! 98.53! 1.15! 94.02! 8.88!
63.42! 94.92! 0.30! 99.07! 1.05! 95.04! 8.10!
69.62! 96.37! 0.30! 99.38! 0.91! 95.73! 7.31!
76.43! 97.49! 0.36! 99.55! 0.75! 96.20! 6.57!
83.90! 98.33! 0.41! 99.65! 0.61! 96.57! 5.94!
92.10! 98.96! 0.42! 99.72! 0.48! 96.89! 5.38!
101.10! 99.41! 0.36! 99.79! 0.36! 97.21! 4.83!
110.99! 99.70! 0.25! 99.86! 0.24! 97.57! 4.21!
121.84! 99.88! 0.14! 99.92! 0.14! 97.98! 3.50!
133.75! 99.96! 0.06! 99.96! 0.06! 98.44! 2.70!
146.82! 99.99! 0.01! 99.99! 0.02! 98.91! 1.89!
161.18! 100.00! 0.00! 100.00! 0.00! 99.33! 1.17!
176.93! ! ! ! ! 99.65! 0.60!
194.23! ! ! ! ! 99.86! 0.24!
213.22! ! ! ! ! 99.96! 0.07!
234.07! ! ! ! ! 99.99! 0.01!
256.95! ! ! ! ! 100.00! 0.00!
&& &
!
!
123!
Grain&Size&(μm)&
TBF&Sample&1& TBF&Sample&2& TBF&Sample&3&Cum&Dist& Std&Dev& Cum&Dist& Std&Dev& Cum&Dist& Std&Dev&
0.41! 0.35! 0.07! 0.37! 0.01! 0.34! 0.00!
0.45! 0.69! 0.14! 0.71! 0.03! 0.66! 0.01!
0.50! 1.16! 0.23! 1.21! 0.05! 1.12! 0.01!
0.54! 1.76! 0.34! 1.82! 0.07! 1.69! 0.02!
0.60! 2.45! 0.45! 2.54! 0.10! 2.36! 0.03!
0.66! 3.23! 0.57! 3.36! 0.13! 3.11! 0.03!
0.72! 4.09! 0.69! 4.27! 0.16! 3.95! 0.04!
0.79! 5.02! 0.79! 5.26! 0.20! 4.84! 0.05!
0.87! 6.01! 0.88! 6.30! 0.24! 5.79! 0.06!
0.95! 7.02! 0.95! 7.39! 0.28! 6.76! 0.08!
1.05! 8.07! 0.99! 8.51! 0.32! 7.76! 0.09!
1.15! 9.13! 1.01! 9.65! 0.36! 8.77! 0.10!
1.26! 10.21! 0.99! 10.82! 0.40! 9.78! 0.12!
1.38! 11.29! 0.95! 11.99! 0.45! 10.79! 0.14!
1.52! 12.37! 0.89! 13.16! 0.49! 11.78! 0.16!
1.67! 13.47! 0.81! 14.35! 0.54! 12.78! 0.18!
1.83! 14.58! 0.72! 15.55! 0.58! 13.78! 0.20!
2.01! 15.72! 0.63! 16.78! 0.63! 14.79! 0.22!
2.21! 16.88! 0.54! 18.03! 0.68! 15.82! 0.25!
2.42! 18.10! 0.46! 19.33! 0.73! 16.87! 0.28!
2.66! 19.37! 0.41! 20.68! 0.78! 17.98! 0.31!
2.92! 20.71! 0.39! 22.10! 0.83! 19.14! 0.35!
3.21! 22.12! 0.39! 23.60! 0.89! 20.37! 0.39!
3.52! 23.63! 0.42! 25.19! 0.95! 21.69! 0.43!
3.86! 25.24! 0.47! 26.88! 1.02! 23.10! 0.47!
4.24! 26.95! 0.53! 28.68! 1.09! 24.62! 0.51!
4.66! 28.75! 0.61! 30.59! 1.17! 26.24! 0.56!
5.11! 30.66! 0.68! 32.61! 1.25! 27.98! 0.60!
5.61! 32.65! 0.76! 34.74! 1.34! 29.82! 0.65!
6.16! 34.73! 0.82! 36.97! 1.44! 31.76! 0.69!
6.76! 36.89! 0.86! 39.30! 1.54! 33.80! 0.74!
7.42! 39.10! 0.87! 41.72! 1.64! 35.94! 0.79!
8.15! 41.38! 0.85! 44.24! 1.75! 38.17! 0.83!
8.94! 43.71! 0.81! 46.86! 1.86! 40.49! 0.88!
9.82! 46.09! 0.75! 49.57! 1.97! 42.89! 0.94!
10.78! 48.52! 0.68! 52.38! 2.08! 45.38! 0.99!
11.83! 50.99! 0.60! 55.30! 2.19! 47.96! 1.04!
12.99! 53.52! 0.54! 58.34! 2.30! 50.63! 1.10!
14.26! 56.11! 0.51! 61.51! 2.40! 53.40! 1.15!
!
!
124!
15.65! 58.77! 0.50! 64.80! 2.49! 56.27! 1.19!
17.18! 61.49! 0.54! 68.19! 2.57! 59.24! 1.22!
18.86! 64.26! 0.59! 71.65! 2.63! 62.29! 1.25!
20.71! 67.04! 0.64! 75.10! 2.67! 65.38! 1.28!
22.73! 69.79! 0.65! 78.47! 2.66! 68.50! 1.29!
24.95! 72.52! 0.62! 81.69! 2.59! 71.63! 1.29!
27.39! 75.21! 0.57! 84.70! 2.46! 74.73! 1.27!
30.07! 77.87! 0.55! 87.47! 2.28! 77.76! 1.22!
33.01! 80.50! 0.57! 89.95! 2.09! 80.69! 1.14!
36.24! 83.08! 0.66! 92.11! 1.91! 83.45! 1.04!
39.78! 85.56! 0.77! 93.92! 1.79! 85.99! 0.92!
43.67! 87.89! 0.87! 95.38! 1.72! 88.25! 0.81!
47.94! 90.00! 0.92! 96.52! 1.70! 90.23! 0.70!
52.63! 91.87! 0.90! 97.37! 1.67! 91.93! 0.59!
57.77! 93.47! 0.82! 98.01! 1.60! 93.38! 0.50!
63.42! 94.81! 0.70! 98.48! 1.48! 94.61! 0.42!
69.62! 95.90! 0.58! 98.85! 1.31! 95.66! 0.36!
76.43! 96.79! 0.49! 99.13! 1.12! 96.53! 0.34!
83.90! 97.52! 0.45! 99.35! 0.95! 97.22! 0.34!
92.10! 98.13! 0.44! 99.50! 0.80! 97.78! 0.33!
101.10! 98.65! 0.43! 99.61! 0.66! 98.23! 0.31!
110.99! 99.10! 0.40! 99.70! 0.51! 98.63! 0.27!
121.84! 99.46! 0.31! 99.79! 0.37! 99.01! 0.23!
133.75! 99.73! 0.19! 99.87! 0.22! 99.37! 0.17!
146.82! 99.90! 0.08! 99.94! 0.11! 99.67! 0.11!
161.18! 99.97! 0.02! 99.98! 0.04! 99.87! 0.05!
176.93! 100.00! 0.00! 100.00! 0.01! 99.97! 0.02!
194.23! ! ! ! ! 100.00! 0.00!
&